--- core/modules/book/src/BookManager.php_BAK	2015-12-02 06:08:29.000000000 -0800
+++ core/modules/book/src/BookManager.php	2016-01-27 14:48:58.328000000 -0800
@@ -404,6 +404,11 @@
       }
     }
 
+    // Return to calling function if all links have been excluded due to depth
+    if (empty($nids)) {
+      return;
+    }
+
     $nodes = $this->entityManager->getStorage('node')->loadMultiple($nids);
 
     foreach ($tree as $data) {