--- modules/book/book.admin.inc.orig	2010-09-27 02:53:56.000000000 +0200
+++ modules/book/book.admin.inc	2010-10-18 16:23:04.000000000 +0200
@@ -106,6 +106,13 @@ function book_admin_edit_validate($form,
 function book_admin_edit_submit($form, &$form_state) {
   // Save elements in the same order as defined in post rather than the form.
   // This ensures parents are updated before their children, preventing orphans.
+
+  // Check that the book contains pages
+  if (empty($form_state['input']['table'])) {
+    drupal_set_message(t('Nothing to update in book %title.', array('%title' => $form['#node']->title)));
+    return;
+  }
+
   $order = array_flip(array_keys($form_state['input']['table']));
   $form['table'] = array_merge($order, $form['table']);