diff --git a/src/calibre/gui2/actions/catalog.py b/src/calibre/gui2/actions/catalog.py
index 0eba0406a1..d75b0dfa5a 100644
--- a/src/calibre/gui2/actions/catalog.py
+++ b/src/calibre/gui2/actions/catalog.py
@@ -57,7 +57,7 @@ class GenerateCatalogAction(InterfaceAction):
         if job.result:
             # Search terms nulled catalog results
             return error_dialog(self.gui, _('No books found'),
-                    _("No books to catalog\nCheck exclusion criteria"),
+                    _("No books to catalog\nCheck job details"),
                     show=True)
         if job.failed:
             return self.gui.job_exception(job)
diff --git a/src/calibre/library/catalog.py b/src/calibre/library/catalog.py
index a9a9caa8db..62d172d6e2 100644
--- a/src/calibre/library/catalog.py
+++ b/src/calibre/library/catalog.py
@@ -1338,7 +1338,8 @@ class EPUB_MOBI(CatalogPlugin):
             if self.booksByTitle is None:
                 if not self.fetchBooksByTitle():
                     return False
-            self.fetchBooksByAuthor()
+            if not self.fetchBooksByAuthor():
+                return False
             self.fetchBookmarks()
             if self.opts.generate_descriptions:
                 self.generateHTMLDescriptions()
@@ -1556,7 +1557,10 @@ class EPUB_MOBI(CatalogPlugin):
                 return False
 
         def fetchBooksByAuthor(self):
-            # Generate a list of titles sorted by author from the database
+            '''
+            Generate a list of titles sorted by author from the database
+            return = Success
+            '''
 
             self.updateProgressFullStep("Sorting database")
 
@@ -1596,10 +1600,16 @@ class EPUB_MOBI(CatalogPlugin):
                     multiple_authors = True
 
                 if author != current_author and i:
-                    # Warn if friendly matches previous, but sort doesn't
+                    # Warn, exit if friendly matches previous, but sort doesn't
                     if author[0] == current_author[0]:
-                        self.opts.log.warn("Warning: multiple entries for Author '%s' with differing Author Sort metadata:" % author[0])
-                        self.opts.log.warn(" '%s' != '%s'" % (author[1], current_author[1]))
+                        error_msg = _("\nWarning: inconsistent Author Sort values for Author '%s', ") % author[0]
+                        error_msg += _("unable to continue building catalog.\n")
+                        error_msg += _("Select all books by '%s', apply same Author Sort value in Edit Metadata dialog, ") % author[0]
+                        error_msg += _("then rebuild the catalog.\n")
+                        error_msg += _("Terminating catalog generation.\n")
+
+                        self.opts.log.warn(error_msg)
+                        return False
 
                     # New author, save the previous author/sort/count
                     unique_authors.append((current_author[0], icu_title(current_author[1]),
@@ -1625,6 +1635,7 @@ class EPUB_MOBI(CatalogPlugin):
                        author[2])).encode('utf-8'))
 
             self.authors = unique_authors
+            return True
 
         def fetchBookmarks(self):
             '''
@@ -1739,8 +1750,6 @@ class EPUB_MOBI(CatalogPlugin):
                 # Generate the header from user-customizable template
                 soup = self.generateHTMLDescriptionHeader(title)
 
-
-
                 # Write the book entry to contentdir
                 outfile = open("%s/book_%d.html" % (self.contentDir, int(title['id'])), 'w')
                 outfile.write(soup.prettify())
@@ -4350,7 +4359,7 @@ class EPUB_MOBI(CatalogPlugin):
                 _soup = BeautifulSoup('')
                 genresTag = Tag(_soup,'p')
                 gtc = 0
-                for (i, tag) in enumerate(book.get('tags', [])):
+                for (i, tag) in enumerate(sorted(book.get('tags', []))):
                     aTag = Tag(_soup,'a')
                     if self.opts.generate_genres:
                         aTag['href'] = "Genre_%s.html" % re.sub("\W","",tag.lower())