diff --git a/flask/game.py b/flask/game.py
index 348ca8c..f004b8c 100755
--- a/flask/game.py
+++ b/flask/game.py
@@ -118,6 +118,9 @@ def push(data, ws):
             db.session.rollback()
             raise AssertionError("you can't push objects into wall.")
         current = objects[y][x]
+        if current is not None and current.get("type", None) == "book":
+            db.session.rollback()
+            raise AssertionError("you can't push objects into books.")
         objects[y][x] = last
         if current is None:
             ok = True