diff --git a/vrobbler/apps/books/models.py b/vrobbler/apps/books/models.py
index 09e9e1c..a41ee44 100644
--- a/vrobbler/apps/books/models.py
+++ b/vrobbler/apps/books/models.py
@@ -184,7 +184,9 @@ class Book(LongPlayScrobblableMixin):
 
     @property
     def subtitle(self):
-        subtitle = self.author
+        subtitle = ""
+        if self.author:
+            subtitle += self.author.name
         if self.issue_number and "Issue" not in str(self.title):
             subtitle += " - Issue {self.issue_number}"
         if self.volume_number and "Volume" not in str(self.title):