diff --git a/src/libprs500/__init__.py b/src/libprs500/__init__.py
index baf0dd8dbf..0b281375fc 100644
--- a/src/libprs500/__init__.py
+++ b/src/libprs500/__init__.py
@@ -13,7 +13,7 @@
 ##    with this program; if not, write to the Free Software Foundation, Inc.,
 ##    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 ''' E-book management software'''
-__version__   = "0.4.6"
+__version__   = "0.4.7"
 __docformat__ = "epytext"
 __author__    = "Kovid Goyal <kovid@kovidgoyal.net>"
 __appname__   = 'libprs500'
diff --git a/src/libprs500/ebooks/metadata/__init__.py b/src/libprs500/ebooks/metadata/__init__.py
index e29692347f..3b1b1c96aa 100644
--- a/src/libprs500/ebooks/metadata/__init__.py
+++ b/src/libprs500/ebooks/metadata/__init__.py
@@ -62,7 +62,7 @@ class MetaInformation(object):
     def __str__(self):
         ans = ''
         ans += 'Title   : ' + str(self.title) + '\n'
-        ans += 'Author  : ' + ', '.join(self.authors) + '\n'
+        ans += 'Author  : ' + (', '.join(self.authors) if self.authors is not None else 'None') + '\n'
         ans += 'Category: ' + str(self.category) + '\n'
         ans += 'Comments: ' + str(self.comments) + '\n'
         return ans.strip()
diff --git a/src/libprs500/gui2/main.py b/src/libprs500/gui2/main.py
index 73cc5e118a..04b57800f8 100644
--- a/src/libprs500/gui2/main.py
+++ b/src/libprs500/gui2/main.py
@@ -269,7 +269,7 @@ class Main(MainWindow, Ui_MainWindow):
     def _add_books(self, paths, to_device):
         on_card = False if self.stack.currentIndex() != 2 else True
         # Get format and metadata information
-        formats, metadata, names, infos = [], [], [], []        
+        formats, metadata, names, infos = [], [], [], []
         for book in paths:
             format = os.path.splitext(book)[1]
             format = format[1:] if format else None
@@ -281,7 +281,7 @@ class Main(MainWindow, Ui_MainWindow):
             metadata.append(mi)
             names.append(os.path.basename(book))
             if not mi.authors:
-                mi.authors = 'Unknown'
+                mi.authors = ['Unknown']
             infos.append({'title':mi.title, 'authors':', '.join(mi.authors), 
                           'cover':self.default_thumbnail, 'tags':[]})
         
diff --git a/src/libprs500/library/database.py b/src/libprs500/library/database.py
index 044988dfef..8be6b433a8 100644
--- a/src/libprs500/library/database.py
+++ b/src/libprs500/library/database.py
@@ -891,15 +891,18 @@ class LibraryDatabase(object):
         '''
         if not append:
             self.conn.execute('DELETE FROM books_tags_link WHERE book=?', (id,))
-        tag = set(tags)
-        for tag in tags:
-            t = self.conn.execute('SELECT id from tags WHERE name=?', (tag,)).fetchone()
+        for tag in set(tags):
+            tag = tag.strip()
+            if not tag:
+                continue
+            t = self.conn.execute('SELECT id FROM tags WHERE name=?', (tag,)).fetchone()
             if t:
                 tid = t[0]
             else:
                 tid = self.conn.execute('INSERT INTO tags(name) VALUES(?)', (tag,)).lastrowid
-            if (append and not self.conn.execute('SELECT book FROM books_tags_link WHERE book=? AND tag=?',
-                                        (id, tid)).fetchone()) or not append:
+            
+            if not self.conn.execute('SELECT book FROM books_tags_link WHERE book=? AND tag=?',
+                                        (id, tid)).fetchone():
                 self.conn.execute('INSERT INTO books_tags_link(book, tag) VALUES (?,?)',
                               (id, tid))
         self.conn.commit()