diff --git a/include/xlnt/cell/cell.hpp b/include/xlnt/cell/cell.hpp
index 941217b8..0b3d40e3 100644
--- a/include/xlnt/cell/cell.hpp
+++ b/include/xlnt/cell/cell.hpp
@@ -426,7 +426,12 @@ public:
     /// <summary>
     /// Returns a wrapper pointing to the named style applied to this cell.
     /// </summary>
-    const class style style() const;
+    class style style();
+
+	/// <summary>
+	/// Returns a wrapper pointing to the named style applied to this cell.
+	/// </summary>
+	const class style style() const;
 
     /// <summary>
     /// Sets the named style applied to this cell to a style named style_name.
diff --git a/include/xlnt/styles/format.hpp b/include/xlnt/styles/format.hpp
index 60b36ddc..0117aabb 100755
--- a/include/xlnt/styles/format.hpp
+++ b/include/xlnt/styles/format.hpp
@@ -43,6 +43,7 @@ namespace detail {
 
 struct format_impl;
 struct stylesheet;
+class xlsx_producer;
 
 } // namespace detail
 
@@ -52,11 +53,6 @@ struct stylesheet;
 class XLNT_API format
 {
 public:
-    /// <summary>
-    ///
-    /// </summary>
-    std::size_t id() const;
-
     // Alignment
 
     /// <summary>
@@ -234,10 +230,16 @@ public:
     /// <summary>
     ///
     /// </summary>
-    const class style style() const;
+    class style style();
+
+	/// <summary>
+	///
+	/// </summary>
+	const class style style() const;
 
 private:
     friend struct detail::stylesheet;
+	friend class detail::xlsx_producer;
     friend class cell;
 
     /// <summary>
@@ -245,6 +247,11 @@ private:
     /// </summary>
     format(detail::format_impl *d);
 
+	/// <summary>
+	///
+	/// </summary>
+	std::size_t id() const;
+
     /// <summary>
     ///
     /// </summary>
diff --git a/include/xlnt/styles/style.hpp b/include/xlnt/styles/style.hpp
index 4fa07d83..c76432b4 100755
--- a/include/xlnt/styles/style.hpp
+++ b/include/xlnt/styles/style.hpp
@@ -61,81 +61,79 @@ public:
     style() = delete;
 
     /// <summary>
-    /// Default copy constructor
+    /// Default copy constructor. Constructs a style using the same PIMPL as other.
     /// </summary>
     style(const style &other) = default;
 
     /// <summary>
-    /// Return the name of this style.
+    /// Returns the name of this style.
     /// </summary>
     std::string name() const;
 
     /// <summary>
-    ///
+    /// Sets the name of this style to name.
     /// </summary>
     style name(const std::string &name);
 
     /// <summary>
-    ///
+    /// Returns true if this style is hidden.
     /// </summary>
     bool hidden() const;
 
     /// <summary>
-    ///
+    /// Sets the hidden state of this style to value. A hidden style will not 
+	/// be shown in the list of selectable styles in the UI, but will still 
+	/// apply its formatting to cells using it.
     /// </summary>
     style hidden(bool value);
 
     /// <summary>
-    ///
+    /// Returns true if this is a builtin style that has been customized and
+	/// should therefore be persisted in the workbook.
     /// </summary>
-    optional<bool> custom() const;
+    bool custom_builtin() const;
 
     /// <summary>
-    ///
+    /// Returns the index of the builtin style that this style is an instance 
+	/// of or is a customized version thereof. If style::builtin() is false,
+	/// this will throw an invalid_attribute exception.
     /// </summary>
-    style custom(bool value);
+    std::size_t builtin_id() const;
+
+	/// <summary>
+	/// Returns true if this is a builtin style.
+	/// </summary>
+	bool builtin() const;
+
+    // Formatting (xf) components
 
     /// <summary>
-    ///
+    /// Returns the alignment of this style.
     /// </summary>
-    optional<std::size_t> builtin_id() const;
+    class alignment alignment() const;
+
+	/// <summary>
+	/// Returns true if the alignment of this style should be applied to cells
+	/// using it.
+	/// </summary>
+	bool alignment_applied() const;
 
     /// <summary>
-    ///
-    /// </summary>
-    style builtin_id(std::size_t builtin_id);
-
-    // Formatting components
-
-    /// <summary>
-    ///
-    /// </summary>
-    class alignment &alignment();
-
-    /// <summary>
-    ///
-    /// </summary>
-    const class alignment &alignment() const;
-
-    /// <summary>
-    ///
+    /// Sets the alignment of this style to new_alignment. Applied, which defaults
+	/// to true, determines whether the alignment should be enabled for cells using
+	/// this style.
     /// </summary>
     style alignment(const xlnt::alignment &new_alignment, bool applied = true);
 
     /// <summary>
     ///
     /// </summary>
-    bool alignment_applied() const;
+    class border border() const;
 
-    /// <summary>
-    ///
-    /// </summary>
-    class border &border();
-
-    /// <summary>
-    ///
-    /// </summary>
-    const class border &border() const;
+	/// <summary>
+	///
+	/// </summary>
+	bool border_applied() const;
 
     /// <summary>
     ///
@@ -145,17 +143,12 @@ public:
     /// <summary>
     ///
     /// </summary>
-    bool border_applied() const;
+    class fill fill() const;
 
-    /// <summary>
-    ///
-    /// </summary>
-    class fill &fill();
-
-    /// <summary>
-    ///
-    /// </summary>
-    const class fill &fill() const;
+	/// <summary>
+	///
+	/// </summary>
+	bool fill_applied() const;
 
     /// <summary>
     ///
@@ -165,17 +158,12 @@ public:
     /// <summary>
     ///
     /// </summary>
-    bool fill_applied() const;
+    class font font() const;
 
-    /// <summary>
-    ///
-    /// </summary>
-    class font &font();
-
-    /// <summary>
-    ///
-    /// </summary>
-    const class font &font() const;
+	/// <summary>
+	///
+	/// </summary>
+	bool font_applied() const;
 
     /// <summary>
     ///
@@ -185,17 +173,12 @@ public:
     /// <summary>
     ///
     /// </summary>
-    bool font_applied() const;
+    class number_format number_format() const;
 
-    /// <summary>
-    ///
-    /// </summary>
-    class number_format &number_format();
-
-    /// <summary>
-    ///
-    /// </summary>
-    const class number_format &number_format() const;
+	/// <summary>
+	///
+	/// </summary>
+	bool number_format_applied() const;
 
     /// <summary>
     ///
@@ -205,53 +188,51 @@ public:
     /// <summary>
     ///
     /// </summary>
-    bool number_format_applied() const;
+    class protection protection() const;
+
+	/// <summary>
+	/// 
+	/// </summary>
+	bool protection_applied() const;
 
     /// <summary>
-    ///
-    /// </summary>
-    class protection &protection();
-
-    /// <summary>
-    ///
-    /// </summary>
-    const class protection &protection() const;
-
-    /// <summary>
-    ///
+    /// 
     /// </summary>
     style protection(const xlnt::protection &new_protection, bool applied = true);
 
     /// <summary>
-    ///
-    /// </summary>
-    bool protection_applied() const;
-
-    /// <summary>
-    ///
+    /// Returns true if the pivot table interface is enabled for this style.
     /// </summary>
     bool pivot_button() const;
 
     /// <summary>
-    ///
+    /// If show is true, a pivot table interface will be displayed for cells using
+	/// this style.
     /// </summary>
     void pivot_button(bool show);
 
     /// <summary>
-    ///
+    /// Returns true if this style should add a single-quote prefix for all text values.
     /// </summary>
     bool quote_prefix() const;
 
     /// <summary>
-    ///
+    /// If quote is true, enables a single-quote prefix for all text values in cells
+	/// using this style (e.g. "abc" will appear as "'abc"). The text will also not
+	/// be stored in sharedStrings when this is enabled.
     /// </summary>
     void quote_prefix(bool quote);
 
     /// <summary>
-    ///
+    /// Returns true if this style is equivalent to other.
     /// </summary>
     bool operator==(const style &other) const;
 
+	/// <summary>
+	/// Returns true if this style is not equivalent to other.
+	/// </summary>
+	bool operator!=(const style &other) const;
+
 private:
     friend struct detail::stylesheet;
     friend class detail::xlsx_consumer;
diff --git a/include/xlnt/workbook/workbook.hpp b/include/xlnt/workbook/workbook.hpp
index 86715b71..01826e88 100644
--- a/include/xlnt/workbook/workbook.hpp
+++ b/include/xlnt/workbook/workbook.hpp
@@ -669,6 +669,11 @@ public:
     /// </summary>
     class style create_style(const std::string &name);
 
+	/// <summary>
+	/// Creates a new style and returns it.
+	/// </summary>
+	class style create_builtin_style(std::size_t builtin_id);
+
     /// <summary>
     /// Clear all named styles from cells and remove the styles from
     /// from the styelsheet. This leaves all other styling in place
diff --git a/source/cell/cell.cpp b/source/cell/cell.cpp
index 559b2cc7..aa5addd3 100644
--- a/source/cell/cell.cpp
+++ b/source/cell/cell.cpp
@@ -792,14 +792,26 @@ void cell::style(const std::string &style_name)
     style(workbook().style(style_name));
 }
 
-const style cell::style() const
+style cell::style()
 {
     if (!has_format() || !format().has_style())
     {
         throw invalid_attribute();
     }
 
-    return format().style();
+	auto f = format();
+
+    return f.style();
+}
+
+const style cell::style() const
+{
+	if (!has_format() || !format().has_style())
+	{
+		throw invalid_attribute();
+	}
+
+	return format().style();
 }
 
 bool cell::has_style() const
diff --git a/source/detail/style_impl.hpp b/source/detail/style_impl.hpp
index ccffa092..49153ae1 100755
--- a/source/detail/style_impl.hpp
+++ b/source/detail/style_impl.hpp
@@ -25,7 +25,7 @@ struct style_impl
 	std::string name;
 	std::size_t formatting_record_id;
 
-	optional<bool> custom_builtin;
+	bool custom_builtin;
 	bool hidden_style;
 
 	optional<std::size_t> builtin_id;
diff --git a/source/detail/stylesheet.hpp b/source/detail/stylesheet.hpp
index f02e4eb9..1e6f6d36 100644
--- a/source/detail/stylesheet.hpp
+++ b/source/detail/stylesheet.hpp
@@ -83,6 +83,71 @@ struct stylesheet
         return xlnt::style(&impl);
     }
 
+	class style create_builtin_style(const std::size_t builtin_id)
+	{
+		// From Annex G.2
+		static const auto *names = new std::unordered_map<std::size_t , std::string>
+		{
+			{ 0, "Normal" },
+			{ 1, "RowLevel_1" },
+			{ 2, "ColLevel_1" },
+			{ 3, "Comma" },
+			{ 4, "Currency" },
+			{ 5, "Percent" },
+			{ 6, "Comma [0]" },
+			{ 7, "Currency [0]" },
+			{ 8, "Hyperlink" },
+			{ 9, "Followed Hyperlink" },
+			{ 10, "Note" },
+			{ 11, "Warning Text" },
+			{ 15, "Title" },
+			{ 16, "Heading 1" },
+			{ 17, "Heading 2" },
+			{ 18, "Heading 3" },
+			{ 19, "Heading 4" },
+			{ 20, "Input" },
+			{ 21, "Output"},
+			{ 22, "Calculation"},
+			{ 22, "Calculation" },
+			{ 23, "Check Cell" },
+			{ 24, "Linked Cell" },
+			{ 25, "Total" },
+			{ 26, "Good" },
+			{ 27, "Bad" },
+			{ 28, "Neutral" },
+			{ 29, "Accent1" },
+			{ 30, "20% - Accent1" },
+			{ 31, "40% - Accent1" },
+			{ 32, "60% - Accent1" },
+			{ 33, "Accent2" },
+			{ 34, "20% - Accent2" },
+			{ 35, "40% - Accent2" },
+			{ 36, "60% - Accent2" },
+			{ 37, "Accent3" },
+			{ 38, "20% - Accent3" },
+			{ 39, "40% - Accent3" },
+			{ 40, "60% - Accent3" },
+			{ 41, "Accent4" },
+			{ 42, "20% - Accent4" },
+			{ 43, "40% - Accent4" },
+			{ 44, "60% - Accent4" },
+			{ 45, "Accent5" },
+			{ 46, "20% - Accent5" },
+			{ 47, "40% - Accent5" },
+			{ 48, "60% - Accent5" },
+			{ 49, "Accent6" },
+			{ 50, "20% - Accent6" },
+			{ 51, "40% - Accent6" },
+			{ 52, "60% - Accent6" },
+			{ 53, "Explanatory Text" }
+		};
+
+		auto new_style = create_style(names->at(builtin_id));
+		new_style.d_->builtin_id = builtin_id;
+
+		return new_style;
+	}
+
     class style style(const std::string &name)
 	{
         if (!has_style(name)) throw key_not_found();
diff --git a/source/detail/xlsx_producer.cpp b/source/detail/xlsx_producer.cpp
index f4c243ac..c28cf6bd 100755
--- a/source/detail/xlsx_producer.cpp
+++ b/source/detail/xlsx_producer.cpp
@@ -1422,10 +1422,10 @@ void xlsx_producer::write_styles(const relationship & /*rel*/)
                 write_attribute("hidden", write_bool(true));
             }
 
-            if (current_style.custom_builtin.is_set())
-            {
-                write_attribute("customBuiltin", write_bool(current_style.custom_builtin.get()));
-            }
+			if (current_style.builtin_id.is_set() && current_style.custom_builtin)
+			{
+				write_attribute("customBuiltin", write_bool(current_style.custom_builtin));
+			}
 
             write_end_element(xmlns, "cellStyle");
         }
diff --git a/source/styles/format.cpp b/source/styles/format.cpp
index 42a5e581..4f1dab3f 100755
--- a/source/styles/format.cpp
+++ b/source/styles/format.cpp
@@ -61,7 +61,7 @@ bool format::has_style() const
     return d_->style.is_set();
 }
 
-const style format::style() const
+style format::style()
 {
     if (!has_style())
     {
@@ -71,6 +71,16 @@ const style format::style() const
     return d_->parent->style(d_->style.get());
 }
 
+const style format::style() const
+{
+	if (!has_style())
+	{
+		throw invalid_attribute();
+	}
+
+	return d_->parent->style(d_->style.get());
+}
+
 xlnt::alignment &format::alignment()
 {
     return d_->parent->alignments.at(d_->alignment_id.get());
diff --git a/source/styles/style.cpp b/source/styles/style.cpp
index d2632f6a..694989e1 100755
--- a/source/styles/style.cpp
+++ b/source/styles/style.cpp
@@ -31,6 +31,17 @@
 #include <xlnt/styles/style.hpp>
 #include <detail/stylesheet.hpp>
 
+namespace {
+
+std::vector<xlnt::number_format>::iterator find_number_format(
+	std::vector<xlnt::number_format> &number_formats, std::size_t id)
+{
+	return std::find_if(number_formats.begin(), number_formats.end(),
+		[=](const xlnt::number_format &nf) { return nf.id() == id; });
+}
+
+}
+
 namespace xlnt {
 
 style::style(detail::style_impl *d)
@@ -49,15 +60,9 @@ style style::hidden(bool value)
     return style(d_);
 }
 
-optional<std::size_t> style::builtin_id() const
+std::size_t style::builtin_id() const
 {
-    return d_->builtin_id;
-}
-
-style style::builtin_id(std::size_t builtin_id)
-{
-    d_->builtin_id = builtin_id;
-    return *this;
+    return d_->builtin_id.get();
 }
 
 std::string style::name() const
@@ -71,15 +76,9 @@ style style::name(const std::string &name)
     return *this;
 }
 
-optional<bool> style::custom() const
+bool style::custom_builtin() const
 {
-    return d_->custom_builtin;
-}
-
-style style::custom(bool value)
-{
-    d_->custom_builtin = value;
-    return *this;
+	return d_->builtin_id.is_set() && d_->custom_builtin;
 }
 
 bool style::operator==(const style &other) const
@@ -87,86 +86,94 @@ bool style::operator==(const style &other) const
     return name() == other.name();
 }
 
-xlnt::alignment &style::alignment()
+xlnt::alignment style::alignment() const
 {
     return d_->parent->alignments.at(d_->alignment_id.get());
 }
 
-const xlnt::alignment &style::alignment() const
+bool style::alignment_applied() const
 {
-    return d_->parent->alignments.at(d_->alignment_id.get());
+	return d_->alignment_applied;
 }
 
 style style::alignment(const xlnt::alignment &new_alignment, bool applied)
 {
     d_->alignment_id = d_->parent->find_or_add(d_->parent->alignments, new_alignment);
     d_->alignment_applied = applied;
-    return style(d_);
+
+	return *this;
 }
 
-xlnt::border &style::border()
+xlnt::border style::border() const
 {
     return d_->parent->borders.at(d_->border_id.get());
 }
 
-const xlnt::border &style::border() const
+bool style::border_applied() const
 {
-    return d_->parent->borders.at(d_->border_id.get());
+	return d_->border_applied;
 }
 
 style style::border(const xlnt::border &new_border, bool applied)
 {
     d_->border_id = d_->parent->find_or_add(d_->parent->borders, new_border);
     d_->border_applied = applied;
-    return style(d_);
+
+	return *this;
 }
 
-xlnt::fill &style::fill()
+xlnt::fill style::fill() const
 {
     return d_->parent->fills.at(d_->fill_id.get());
 }
 
-const xlnt::fill &style::fill() const
+bool style::fill_applied() const
 {
-    return d_->parent->fills.at(d_->fill_id.get());
+	return d_->fill_applied;
 }
 
 style style::fill(const xlnt::fill &new_fill, bool applied)
 {
     d_->fill_id = d_->parent->find_or_add(d_->parent->fills, new_fill);
     d_->fill_applied = applied;
-    return style(d_);
+
+	return *this;
 }
 
-xlnt::font &style::font()
+xlnt::font style::font() const
 {
     return d_->parent->fonts.at(d_->font_id.get());
 }
 
-const xlnt::font &style::font() const
+bool style::font_applied() const
 {
-    return d_->parent->fonts.at(d_->font_id.get());
+	return d_->font_applied;
 }
 
 style style::font(const xlnt::font &new_font, bool applied)
 {
     d_->font_id = d_->parent->find_or_add(d_->parent->fonts, new_font);
     d_->font_applied = applied;
-    return style(d_);
+
+	return *this;
 }
 
-xlnt::number_format &style::number_format()
+xlnt::number_format style::number_format() const
 {
-    auto tarid = d_->number_format_id.get();
-    return *std::find_if(d_->parent->number_formats.begin(), d_->parent->number_formats.end(),
-        [=](const class number_format &nf) { return nf.id() == tarid; });
+	auto match = find_number_format(d_->parent->number_formats, 
+		d_->number_format_id.get());
+
+	if (match == d_->parent->number_formats.end())
+	{
+		throw invalid_attribute();
+	}
+
+	return *match;
 }
 
-const xlnt::number_format &style::number_format() const
+bool style::number_format_applied() const
 {
-    auto tarid = d_->number_format_id.get();
-    return *std::find_if(d_->parent->number_formats.begin(), d_->parent->number_formats.end(),
-        [=](const class number_format &nf) { return nf.id() == tarid; });
+	return d_->number_format_applied;
 }
 
 style style::number_format(const xlnt::number_format &new_number_format, bool applied)
@@ -178,64 +185,34 @@ style style::number_format(const xlnt::number_format &new_number_format, bool ap
         copy.id(d_->parent->next_custom_number_format_id());
         d_->parent->number_formats.push_back(copy);
     }
-    else if (std::find_if(d_->parent->number_formats.begin(), d_->parent->number_formats.end(),
-                 [&copy](const class number_format &nf) { return nf.id() == copy.id(); })
-        == d_->parent->number_formats.end())
-    {
+	else if (find_number_format(d_->parent->number_formats, copy.id()) 
+		== d_->parent->number_formats.end())
+	{
         d_->parent->number_formats.push_back(copy);
     }
 
     d_->number_format_id = copy.id();
     d_->number_format_applied = applied;
 
-    return style(d_);
+	return *this;
 }
 
-xlnt::protection &style::protection()
+xlnt::protection style::protection() const
 {
     return d_->parent->protections.at(d_->protection_id.get());
 }
 
-const xlnt::protection &style::protection() const
+bool style::protection_applied() const
 {
-    return d_->parent->protections.at(d_->protection_id.get());
+	return d_->protection_applied;
 }
 
 style style::protection(const xlnt::protection &new_protection, bool applied)
 {
     d_->protection_id = d_->parent->find_or_add(d_->parent->protections, new_protection);
     d_->protection_applied = applied;
-    return style(d_);
-}
 
-bool style::alignment_applied() const
-{
-    return d_->alignment_applied;
-}
-
-bool style::border_applied() const
-{
-    return d_->border_applied;
-}
-
-bool style::fill_applied() const
-{
-    return d_->fill_applied;
-}
-
-bool style::font_applied() const
-{
-    return d_->font_applied;
-}
-
-bool style::number_format_applied() const
-{
-    return d_->number_format_applied;
-}
-
-bool style::protection_applied() const
-{
-    return d_->protection_applied;
+    return *this;
 }
 
 bool style::pivot_button() const
diff --git a/source/workbook/workbook.cpp b/source/workbook/workbook.cpp
index 7a3dfcab..59449471 100644
--- a/source/workbook/workbook.cpp
+++ b/source/workbook/workbook.cpp
@@ -497,12 +497,7 @@ workbook workbook::empty()
         .color(theme_color(1));
     stylesheet.fonts.push_back(default_font);
 
-    wb.create_style("Normal")
-        .builtin_id(0)
-        .border(default_border, false)
-        .fill(default_fill, false)
-        .font(default_font, false)
-        .number_format(xlnt::number_format::general(), false);
+	wb.create_builtin_style(0);
 
     wb.create_format(true)
         .border(default_border, false)
@@ -1351,6 +1346,11 @@ style workbook::create_style(const std::string &name)
     return d_->stylesheet_.get().create_style(name);
 }
 
+style workbook::create_builtin_style(const std::size_t builtin_id)
+{
+	return d_->stylesheet_.get().create_builtin_style(builtin_id);
+}
+
 style workbook::style(const std::string &name)
 {
     return d_->stylesheet_.get().style(name);