diff --git a/core/modules/book/src/BookManager.php b/core/modules/book/src/BookManager.php
index 6f0ae24..03ff784 100644
--- a/core/modules/book/src/BookManager.php
+++ b/core/modules/book/src/BookManager.php
@@ -283,6 +283,31 @@ public function updateOutline(NodeInterface $node) {
     $updated = !$new && (($original = $this->loadBookLink($node->id(), FALSE)) && ($node->book['bid'] != $original['bid'] || $node->book['pid'] != $original['pid']));
     if (($new || $updated) && !$node->isDefaultRevision()) {
       drupal_set_message($this->t('This is not the default revision. You can only change the book outline for the <em>published</em> version of this content.'), 'error');
+
+      // Improve the usability of the error message by showing the changes that
+      // could not be applied.
+      if ($updated) {
+        $changes = [];
+        $new_parents = $this->loadBookLinks([$node->book['bid'], $node->book['pid']]);
+        if ($node->book['bid'] != $original['bid'] && $new_parents[$node->book['bid']]['access']) {
+          $changes[] = $this->t('The book was not changed to %book_label', ['%book_label' => $new_parents[$node->book['bid']]['title']]);
+        }
+        if ($node->book['pid'] != $original['pid'] && $new_parents[$node->book['pid']]['access']) {
+          $changes[] = $this->t('The parent was not changed to %parent_label', ['%parent_label' => $new_parents[$node->book['pid']]['title']]);
+        }
+
+        $message = [
+          [
+            '#markup' => $this->t('The following changes were not applied:')
+          ],
+          [
+            '#theme' => 'item_list',
+            '#items' => $changes,
+          ]
+        ];
+        drupal_set_message($this->renderer->renderPlain($message), 'warning');
+      }
+
       return FALSE;
     }