diff -u b/core/modules/book/src/BookManager.php b/core/modules/book/src/BookManager.php
--- b/core/modules/book/src/BookManager.php
+++ b/core/modules/book/src/BookManager.php
@@ -598,7 +598,8 @@
    *     Defaults to 1, which is to build the whole tree for the book.
    *   - max_depth: The maximum depth of book links in the resulting tree.
    *   - conditions: An associative array of custom database select query
-   *     condition key/value pairs; see \Drupal\book\BookOutlineStorage::getBookMenuTree()
+   *     condition key/value pairs; see
+   *     \Drupal\book\BookOutlineStorage::getBookMenuTree()
    *     for the actual query.
    *
    * @return array
@@ -634,7 +635,8 @@
    *     Defaults to 1, which is to build the whole tree for the book.
    *   - max_depth: The maximum depth of book links in the resulting tree.
    *   - conditions: An associative array of custom database select query
-   *     condition key/value pairs; see \Drupal\book\BookOutlineStorage::getBookMenuTree()
+   *     condition key/value pairs; see
+   *     \Drupal\book\BookOutlineStorage::getBookMenuTree()
    *     for the actual query.
    *
    * @return array