diff --git a/manual/edit.rst b/manual/edit.rst
index 45bcd17fe2..3475b54a3d 100644
--- a/manual/edit.rst
+++ b/manual/edit.rst
@@ -335,6 +335,15 @@ Note that the algorithm can sometimes generate incorrect results, especially
 when single quotes at the start of contractions are involved. Accessed via
 :guilabel:`Tools->Smarten punctuation`.
 
+Removing unused CSS rules
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Remove all unused CSS rules from stylesheets and <style> tags. Some books
+created from production templates can have a large number of extra CSS rules
+that dont match any actual content. These extra rules can slow down readers
+that need to process them all. Accessed via :guilabel:`Tools->Remove unused CSS`.
+
+
 Fix HTML
 ^^^^^^^^^^^
 
diff --git a/src/calibre/ebooks/oeb/polish/css.py b/src/calibre/ebooks/oeb/polish/css.py
new file mode 100644
index 0000000000..954d4a1566
--- /dev/null
+++ b/src/calibre/ebooks/oeb/polish/css.py
@@ -0,0 +1,149 @@
+#!/usr/bin/env python
+# vim:fileencoding=utf-8
+from __future__ import (unicode_literals, division, absolute_import,
+                        print_function)
+
+__license__ = 'GPL v3'
+__copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
+
+import re
+
+from lxml import etree
+from cssselect import HTMLTranslator
+from cssselect.xpath import XPathExpr, is_safe_name
+
+from calibre import force_unicode
+from calibre.ebooks.oeb.base import OEB_STYLES, OEB_DOCS, XPNSMAP, XHTML_NS
+from calibre.ebooks.oeb.stylizer import MIN_SPACE_RE, is_non_whitespace, xpath_lower_case, fix_namespace
+from calibre.ebooks.oeb.polish.pretty import pretty_script_or_style
+
+class NamespacedTranslator(HTMLTranslator):
+
+    def xpath_element(self, selector):
+        element = selector.element
+        if not element:
+            element = '*'
+            safe = True
+        else:
+            safe = is_safe_name(element)
+            if safe:
+                # We use the h: prefix for the XHTML namespace
+                element = 'h:%s' % element.lower()
+        xpath = XPathExpr(element=element)
+        if not safe:
+            xpath.add_name_test()
+        return xpath
+
+class CaseInsensitiveAttributesTranslator(NamespacedTranslator):
+    'Treat class and id CSS selectors case-insensitively'
+
+    def xpath_class(self, class_selector):
+        """Translate a class selector."""
+        x = self.xpath(class_selector.selector)
+        if is_non_whitespace(class_selector.class_name):
+            x.add_condition(
+                "%s and contains(concat(' ', normalize-space(%s), ' '), %s)"
+                % ('@class', xpath_lower_case('@class'), self.xpath_literal(
+                    ' '+class_selector.class_name.lower()+' ')))
+        else:
+            x.add_condition('0')
+        return x
+
+    def xpath_hash(self, id_selector):
+        """Translate an ID selector."""
+        x = self.xpath(id_selector.selector)
+        return self.xpath_attrib_equals(x, xpath_lower_case('@id'),
+                (id_selector.id.lower()))
+
+css_to_xpath = NamespacedTranslator().css_to_xpath
+ci_css_to_xpath = CaseInsensitiveAttributesTranslator().css_to_xpath
+
+def build_selector(text, case_sensitive=True):
+    func = css_to_xpath if case_sensitive else ci_css_to_xpath
+    try:
+        return etree.XPath(fix_namespace(func(text)), namespaces=XPNSMAP)
+    except Exception:
+        return None
+
+def is_rule_used(root, selector, log, pseudo_pat, cache):
+    selector = pseudo_pat.sub('', selector)
+    selector = MIN_SPACE_RE.sub(r'\1', selector)
+    try:
+        xp = cache[(True, selector)]
+    except KeyError:
+        xp = cache[(True, selector)] = build_selector(selector)
+    try:
+        if xp(root):
+            return True
+    except Exception:
+        return True
+
+    # See if interpreting class and id selectors case-insensitively gives us
+    # matches. Strictly speaking, class and id selectors should be case
+    # sensitive for XHTML, but we err on the side of caution and not remove
+    # them, since case sensitivity depends on whether the html is rendered in
+    # quirks mode or not.
+    try:
+        xp = cache[(False, selector)]
+    except KeyError:
+        xp = cache[(False, selector)] = build_selector(selector, case_sensitive=False)
+    try:
+        return bool(xp(root))
+    except Exception:
+        return True
+
+def filter_used_rules(root, rules, log, pseudo_pat, cache):
+    for rule in rules:
+        used = False
+        for selector in rule.selectorList:
+            text = selector.selectorText
+            if is_rule_used(root, text, log, pseudo_pat, cache):
+                used = True
+                break
+        if not used:
+            yield rule
+
+def remove_unused_css(container, report):
+    from cssutils.css import CSSRule
+    sheets = {name:container.parsed(name) for name, mt in container.mime_map.iteritems() if mt in OEB_STYLES}
+    for sheet in sheets.itervalues():
+        sheet.namespaces['h'] = XHTML_NS
+    style_rules = {name:tuple(sheet.cssRules.rulesOfType(CSSRule.STYLE_RULE)) for name, sheet in sheets.iteritems()}
+
+    num_of_removed_rules = 0
+    pseudo_pat = re.compile(r':(first-letter|first-line|link|hover|visited|active|focus|before|after)', re.I)
+    cache = {}
+
+    for name, mt in container.mime_map.iteritems():
+        if mt not in OEB_DOCS:
+            continue
+        root = container.parsed(name)
+        for style in root.xpath('//*[local-name()="style"]'):
+            if style.get('type', 'text/css') == 'text/css' and style.text:
+                sheet = container.parse_css(style.text)
+                sheet.namespaces['h'] = XHTML_NS
+                rules = tuple(sheet.cssRules.rulesOfType(CSSRule.STYLE_RULE))
+                unused_rules = tuple(filter_used_rules(root, rules, container.log, pseudo_pat, cache))
+                if unused_rules:
+                    num_of_removed_rules += len(unused_rules)
+                    [sheet.cssRules.remove(r) for r in unused_rules]
+                    style.text = force_unicode(sheet.cssText, 'utf-8')
+                    pretty_script_or_style(container, style)
+                    container.dirty(name)
+
+        for link in root.xpath('//*[local-name()="link" and @href]'):
+            sname = container.href_to_name(link.get('href'), name)
+            if sname in sheets:
+                style_rules[sname] = tuple(filter_used_rules(root, style_rules[sname], container.log, pseudo_pat, cache))
+
+    for name, sheet in sheets.iteritems():
+        unused_rules = style_rules[name]
+        if unused_rules:
+            num_of_removed_rules += len(unused_rules)
+            [sheet.cssRules.remove(r) for r in unused_rules]
+            container.dirty(name)
+
+    if num_of_removed_rules > 0:
+        report(_('Removed %d unused CSS style rules') % num_of_removed_rules)
+    else:
+        report(_('No unused CSS style rules found'))
diff --git a/src/calibre/ebooks/oeb/polish/main.py b/src/calibre/ebooks/oeb/polish/main.py
index 19d3386c84..dd6ecf15b4 100644
--- a/src/calibre/ebooks/oeb/polish/main.py
+++ b/src/calibre/ebooks/oeb/polish/main.py
@@ -19,6 +19,7 @@ from calibre.ebooks.oeb.polish.cover import set_cover
 from calibre.ebooks.oeb.polish.replace import smarten_punctuation
 from calibre.ebooks.oeb.polish.jacket import (
     replace_jacket, add_or_replace_jacket, find_existing_jacket, remove_jacket)
+from calibre.ebooks.oeb.polish.css import remove_unused_css
 from calibre.utils.logging import Log
 
 ALL_OPTS = {
@@ -29,6 +30,7 @@ ALL_OPTS = {
     'jacket': False,
     'remove_jacket':False,
     'smarten_punctuation':False,
+    'remove_unused_css':False,
 }
 
 SUPPORTED = {'EPUB', 'AZW3'}
@@ -90,6 +92,13 @@ typographically correct equivalents.</p>
 <p>Note that the algorithm can sometimes generate incorrect results, especially
 when single quotes at the start of contractions are involved.</p>
 '''),
+
+'remove_unused_css': _('''\
+<p>Remove all unused CSS rules from stylesheets and &lt;style&gt; tags. Some books
+created from production templates can have a large number of extra CSS rules
+that dont match any actual content. These extra rules can slow down readers
+that need to parse them all.</p>
+'''),
 }
 
 def hfix(name, raw):
@@ -98,6 +107,7 @@ def hfix(name, raw):
     raw = raw.replace('\n\n', '__XX__')
     raw = raw.replace('\n', ' ')
     raw = raw.replace('__XX__', '\n')
+    raw = raw.replace('&lt;', '<').replace('&gt;', '>')
     return raw
 
 CLI_HELP = {x:hfix(x, re.sub('<.*?>', '', y)) for x, y in HELP.iteritems()}
@@ -174,6 +184,11 @@ def polish_one(ebook, opts, report):
         subset_all_fonts(ebook, stats.font_stats, report)
         report('')
 
+    if opts.remove_unused_css:
+        rt(_('Removing unused CSS rules'))
+        remove_unused_css(ebook, report)
+        report('')
+
 
 def polish(file_map, opts, log, report):
     st = time.time()
@@ -233,6 +248,7 @@ def option_parser():
     o('--jacket', '-j', help=CLI_HELP['jacket'])
     o('--remove-jacket', help=CLI_HELP['remove_jacket'])
     o('--smarten-punctuation', '-p', help=CLI_HELP['smarten_punctuation'])
+    o('--remove-unused-css', '-u', help=CLI_HELP['remove_unused_css'])
 
     o('--verbose', help=_('Produce more verbose output, useful for debugging.'))
 
diff --git a/src/calibre/gui2/actions/polish.py b/src/calibre/gui2/actions/polish.py
index 9a4678fbea..69c8d6fc23 100644
--- a/src/calibre/gui2/actions/polish.py
+++ b/src/calibre/gui2/actions/polish.py
@@ -59,13 +59,14 @@ class Polish(QDialog):  # {{{
                          ' formats are not capable of supporting all the'
                          ' metadata in calibre.</p><p>There is a separate option to'
                          ' update the cover.</p>'),
-            'do_cover': _('<p>Update the covers in the ebook files to match the'
+            'do_cover': _('<h3>Update cover</h3><p>Update the covers in the ebook files to match the'
                         ' current cover in the calibre library.</p>'
                         '<p>If the ebook file does not have'
                         ' an identifiable cover, a new cover is inserted.</p>'
                         ),
             'jacket':_('<h3>Book Jacket</h3>%s')%HELP['jacket'],
             'remove_jacket':_('<h3>Remove Book Jacket</h3>%s')%HELP['remove_jacket'],
+            'remove_unused_css':_('<h3>Remove unused CSS rules</h3>%s')%HELP['remove_unused_css'],
         }
 
         self.l = l = QGridLayout()
@@ -83,6 +84,7 @@ class Polish(QDialog):  # {{{
             ('do_cover', _('Update the &cover in the book files')),
             ('jacket', _('Add metadata as a "book &jacket" page')),
             ('remove_jacket', _('&Remove a previously inserted book jacket')),
+            ('remove_unused_css', _('Remove &unused CSS rules from the book')),
         ])
         prefs = gprefs.get('polishing_settings', {})
         for name, text in self.all_actions.iteritems():
diff --git a/src/calibre/gui2/tweak_book/ui.py b/src/calibre/gui2/tweak_book/ui.py
index c22580f289..3fa558a137 100644
--- a/src/calibre/gui2/tweak_book/ui.py
+++ b/src/calibre/gui2/tweak_book/ui.py
@@ -341,6 +341,9 @@ class Main(MainWindow):
         self.action_smarten_punctuation = reg(
             'smarten-punctuation.png', _('&Smarten punctuation'), partial(
                 self.boss.polish, 'smarten_punctuation', _('Smarten punctuation')), 'smarten-punctuation', (), _('Smarten punctuation'))
+        self.action_remove_unused_css = reg(
+            'edit-clear.png', _('Remove &unused CSS rules'), partial(
+                self.boss.polish, 'remove_unused_css', _('Remove unused CSS rules')), 'remove-unused-css', (), _('Remove unused CSS rules'))
 
         # Preview actions
         group = _('Preview')
@@ -440,6 +443,7 @@ class Main(MainWindow):
         e.addAction(self.action_embed_fonts)
         e.addAction(self.action_subset_fonts)
         e.addAction(self.action_smarten_punctuation)
+        e.addAction(self.action_remove_unused_css)
         e.addAction(self.action_fix_html_all)
         e.addAction(self.action_pretty_all)
         e.addAction(self.action_rationalize_folders)
@@ -519,7 +523,7 @@ class Main(MainWindow):
         a(self.action_help)
 
         a = create(_('Polish book tool bar'), 'polish').addAction
-        for x in ('embed_fonts', 'subset_fonts', 'smarten_punctuation'):
+        for x in ('embed_fonts', 'subset_fonts', 'smarten_punctuation', 'remove_unused_css'):
             a(getattr(self, 'action_' + x))
 
     def create_docks(self):