diff --git a/src/main/java/org/ntlab/citrusserver/repositories/IBookListener.java b/src/main/java/org/ntlab/citrusserver/repositories/IBookListener.java
new file mode 100644
index 0000000..c2f3b94
--- /dev/null
+++ b/src/main/java/org/ntlab/citrusserver/repositories/IBookListener.java
@@ -0,0 +1,10 @@
+package org.ntlab.citrusserver.repositories;
+
+import org.ntlab.citrusserver.entities.Account;
+import org.ntlab.citrusserver.entities.Book;
+
+public interface IBookListener {
+
+    void bookChanged(Account account, Book book);
+
+}