Index: modules/book/book.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/book/book.module,v
retrieving revision 1.479
diff -u -p -r1.479 book.module
--- modules/book/book.module	16 Dec 2008 23:57:32 -0000	1.479
+++ modules/book/book.module	17 Dec 2008 01:17:13 -0000
@@ -174,7 +174,17 @@ function _book_outline_access($node) {
  * Menu item access callback - determine if the user can remove nodes from the outline.
  */
 function _book_outline_remove_access($node) {
-  return isset($node->book) && ($node->book['bid'] != $node->nid) && _book_outline_access($node);
+  return _book_node_is_removable($node) && _book_outline_access($node);
+}
+    
+/**
+ * Helper function - determine if a node can be removed from the book.
+ *
+ * A node can only be removed if it's actually in a book, and not a top-level
+ * page, or it is a top-level page with no children.
+ */
+function _book_node_is_removable($node) {
+  return (!empty($node->book['bid']) && (($node->book['bid'] != $node->nid) || !$node->book['has_children']));
 }
 
 /**
Index: modules/book/book.pages.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/book/book.pages.inc,v
retrieving revision 1.12
diff -u -p -r1.12 book.pages.inc
--- modules/book/book.pages.inc	16 Nov 2008 15:02:45 -0000	1.12
+++ modules/book/book.pages.inc	17 Dec 2008 01:17:13 -0000
@@ -130,7 +130,7 @@ function book_outline_form(&$form_state,
   $form['remove'] = array(
     '#type' => 'submit',
     '#value' => t('Remove from book outline'),
-    '#access' => $node->nid != $node->book['bid'] && $node->book['bid'],
+    '#access' => _book_node_is_removable($node),
     '#weight' => 20,
     '#submit' => array('book_remove_button_submit'),
   );
@@ -207,8 +207,9 @@ function book_remove_form(&$form_state, 
  */
 function book_remove_form_submit($form, &$form_state) {
   $node = $form['#node'];
-  if ($node->nid != $node->book['bid']) {
-    // Only allowed when this is not a book (top-level page).
+  if (_book_node_is_removable($node)) {
+    // Only allowed when this is not a book (top-level page),
+    // or for a top-level page with no children.
     menu_link_delete($node->book['mlid']);
     db_delete('book')
       ->condition('nid', $node->nid)