diff --git a/main.py b/main.py
index e175f68..9641666 100644
--- a/main.py
+++ b/main.py
@@ -94,7 +94,7 @@ def api_collection_books(name):
 @app.route('/v1/collections/<string:name>/books/<string:bookNumber>', methods=['GET'])
 def api_collection_book(name, bookNumber):
     number_id_map = {v: k for k, v in Book.id_number_map.items()}
-    bookID = number_id_map[bookNumber] if self.ourBookID in number_id_map else int(bookNumber)
+    bookID = number_id_map.get(bookNumber, int(bookNumber))
     book = Book.query.filter_by(collection=name).filter_by(ourBookID=bookID).first_or_404();
     return jsonify(book.serialize())
 
diff --git a/models.py b/models.py
index 0eb0bb0..9a77395 100644
--- a/models.py
+++ b/models.py
@@ -38,7 +38,7 @@ class Book(db.Model):
 
     def serialize(self):
         # Logic for dealing with non-straightforward ourBookIDs
-        bookNumber = id_number_map[self.ourBookID] if self.ourBookID in id_number_map else str(self.ourBookID)
+        bookNumber = self.id_number_map.get(self.ourBookID, str(self.ourBookID))
         return {
             'bookNumber': bookNumber,
             'book': [