diff --git a/resources/default_tweaks.py b/resources/default_tweaks.py
index ee2e07f412..a15cb62aaf 100644
--- a/resources/default_tweaks.py
+++ b/resources/default_tweaks.py
@@ -496,3 +496,9 @@ gui_view_history_size = 15
 # prefer HTMLZ to EPUB for tweaking, change this to 'htmlz'
 tweak_book_prefer = 'epub'
 
+#: Change the font size of book details in the interface
+# Change the font size at which book details are rendered in the side panel and
+# comments are rendered in the metadata edit dialog. Set it to a positive or
+# negative number to increase or decrease the font size.
+change_book_details_font_size_by = 0
+
diff --git a/src/calibre/gui2/book_details.py b/src/calibre/gui2/book_details.py
index 08df7007a2..4b12335fe3 100644
--- a/src/calibre/gui2/book_details.py
+++ b/src/calibre/gui2/book_details.py
@@ -25,6 +25,7 @@ from calibre.utils.icu import sort_key
 from calibre.utils.formatter import EvalFormatter
 from calibre.utils.date import is_date_undefined
 from calibre.utils.localization import calibre_langcode_to_name
+from calibre.utils.config import tweaks
 
 def render_html(mi, css, vertical, widget, all_fields=False): # {{{
     table = render_data(mi, all_fields=all_fields,
@@ -39,7 +40,7 @@ def render_html(mi, css, vertical, widget, all_fields=False): # {{{
         return ans
 
     fi = QFontInfo(QApplication.font(widget))
-    f = fi.pixelSize()+1
+    f = fi.pixelSize() + 1 + int(tweaks['change_book_details_font_size_by'])
     fam = unicode(fi.family()).strip().replace('"', '')
     if not fam:
         fam = 'sans-serif'
diff --git a/src/calibre/gui2/comments_editor.py b/src/calibre/gui2/comments_editor.py
index e58b7117c1..1324a3cbd4 100644
--- a/src/calibre/gui2/comments_editor.py
+++ b/src/calibre/gui2/comments_editor.py
@@ -19,6 +19,7 @@ from calibre.ebooks.chardet import xml_to_unicode
 from calibre import xml_replace_entities
 from calibre.gui2 import open_url
 from calibre.utils.soupparser import fromstring
+from calibre.utils.config import tweaks
 
 class PageAction(QAction): # {{{
 
@@ -252,7 +253,7 @@ class EditorWidget(QWebView): # {{{
         def fset(self, val):
             self.setHtml(val)
             fi = QFontInfo(QApplication.font(self))
-            f  = fi.pixelSize()+1
+            f  = fi.pixelSize() + 1 + int(tweaks['change_book_details_font_size_by'])
             fam = unicode(fi.family()).strip().replace('"', '')
             if not fam:
                 fam = 'sans-serif'
diff --git a/src/calibre/gui2/metadata/single_download.py b/src/calibre/gui2/metadata/single_download.py
index 6149c3be8a..095b57af60 100644
--- a/src/calibre/gui2/metadata/single_download.py
+++ b/src/calibre/gui2/metadata/single_download.py
@@ -32,6 +32,8 @@ from calibre.utils.date import (utcnow, fromordinal, format_date,
         UNDEFINED_DATE, as_utc)
 from calibre.library.comments import comments_to_html
 from calibre import force_unicode
+from calibre.utils.config import tweaks
+
 # }}}
 
 class RichTextDelegate(QStyledItemDelegate): # {{{
@@ -326,7 +328,7 @@ class Comments(QWebView): # {{{
             return ans
 
         fi = QFontInfo(QApplication.font(self.parent()))
-        f = fi.pixelSize()+1
+        f = fi.pixelSize()+1+int(tweaks['change_book_details_font_size_by'])
         fam = unicode(fi.family()).strip().replace('"', '')
         if not fam:
             fam = 'sans-serif'