diff --git a/core/modules/book/book.module b/core/modules/book/book.module
index 9eecf7a..925547c 100644
--- a/core/modules/book/book.module
+++ b/core/modules/book/book.module
@@ -237,7 +237,7 @@ function _book_outline_access(EntityInterface $node) {
  * @see book_menu()
  */
 function _book_outline_remove_access(EntityInterface $node) {
-  return Drupal::service('book.manager')->nodeIsRemovable($node)
+  return Drupal::service('book.manager')->checkNodeIsRemovable($node)
     && _book_outline_access($node);
 }
 
@@ -637,7 +637,7 @@ function book_node_prepare_form(NodeInterface $node, $form_display, $operation,
     }
     // Set defaults.
     $node_ref = !$node->isNew() ? $node->id() : 'new';
-    $node->book += $book_manager->linkDefaults($node_ref);
+    $node->book += $book_manager->getLinkDefaults($node_ref);
   }
   else {
     if (isset($node->book['bid']) && !isset($node->book['original_bid'])) {
@@ -646,7 +646,7 @@ function book_node_prepare_form(NodeInterface $node, $form_display, $operation,
   }
   // Find the depth limit for the parent select.
   if (isset($node->book['bid']) && !isset($node->book['parent_depth_limit'])) {
-    $node->book['parent_depth_limit'] = $book_manager->parentDepthLimit($node->book);
+    $node->book['parent_depth_limit'] = $book_manager->getParentDepthLimit($node->book);
   }
 }
 
diff --git a/core/modules/book/book.pages.inc b/core/modules/book/book.pages.inc
index 32c7852..40e44b2 100644
--- a/core/modules/book/book.pages.inc
+++ b/core/modules/book/book.pages.inc
@@ -50,7 +50,7 @@ function book_remove_form($form, &$form_state, EntityInterface $node) {
  */
 function book_remove_form_submit($form, &$form_state) {
   $node = $form['#node'];
-  if (Drupal::service('book.manager')->nodeIsRemovable($node)) {
+  if (Drupal::service('book.manager')->checkNodeIsRemovable($node)) {
     menu_link_delete($node->book['mlid']);
     db_delete('book')
       ->condition('nid', $node->id())
diff --git a/core/modules/book/lib/Drupal/book/BookManager.php b/core/modules/book/lib/Drupal/book/BookManager.php
index 2a6834d..f10630b 100644
--- a/core/modules/book/lib/Drupal/book/BookManager.php
+++ b/core/modules/book/lib/Drupal/book/BookManager.php
@@ -123,7 +123,7 @@ protected function loadBooks() {
    * @return array
    *   The default values for the menu link.
    */
-  public function linkDefaults($nid) {
+  public function getLinkDefaults($nid) {
     return array(
       'original_bid' => 0,
       'menu_name' => '',
@@ -148,7 +148,7 @@ public function linkDefaults($nid) {
    * @return int
    *   The depth limit for items in the parent select.
    */
-  public function parentDepthLimit($book_link) {
+  public function getParentDepthLimit(array $book_link) {
     return MENU_MAX_DEPTH - 1 - (($book_link['mlid'] && $book_link['has_children']) ? $this->entityManager->getStorageController('menu_link')->findChildrenRelativeDepth($book_link) : 0);
   }
 
@@ -258,7 +258,7 @@ public function addFormElements(array $form, array &$form_state, NodeInterface $
    * @return bool
    *   TRUE if a node can be removed from the book, FALSE otherwise.
    */
-  public function nodeIsRemovable(NodeInterface $node) {
+  public function checkNodeIsRemovable(NodeInterface $node) {
     return (!empty($node->book['bid']) && (($node->book['bid'] != $node->id()) || !$node->book['has_children']));
   }
 
@@ -316,8 +316,6 @@ public function updateOutline(NodeInterface $node) {
             'bid' => $node->book['bid'],
           ))
           ->execute();
-        // Reset the cache of stored books.
-        drupal_static_reset('book_get_books');
       }
       else {
         if ($node->book['bid'] != $this->connection->query("SELECT bid FROM {book} WHERE nid = :nid", array(
@@ -325,8 +323,6 @@ public function updateOutline(NodeInterface $node) {
         ))->fetchField()) {
           // Update the bid for this page and all children.
           $this->updateID($node->book);
-          // Reset the cache of stored books.
-          drupal_static_reset('book_get_books');
         }
       }
 
@@ -380,7 +376,7 @@ public function createMenuName($id) {
    * @param array $book_link
    *   A fully loaded menu link that is part of the book hierarchy.
    */
-  function updateID($book_link) {
+  public function updateID(array $book_link) {
     $query = $this->connection->select('menu_links');
     $query->addField('menu_links', 'mlid');
     for ($i = 1; $i <= MENU_MAX_DEPTH && $book_link["p$i"]; $i++) {
@@ -409,7 +405,7 @@ function updateID($book_link) {
    * @return array
    *   A parent selection form element.
    */
-  function addParentSelectFormElements($book_link) {
+  protected function addParentSelectFormElements(array $book_link) {
     if ($this->configFactory->get('menu.settings')->get('override_parent_selector')) {
       return array();
     }
@@ -471,7 +467,7 @@ function addParentSelectFormElements($book_link) {
    * @param int $depth_limit
    *   Any link deeper than this value will be excluded (along with its children).
    */
-  protected function recurseTableOfContents($tree, $indent, &$toc, $exclude, $depth_limit) {
+  protected function recurseTableOfContents(array $tree, $indent, array &$toc, array $exclude, $depth_limit) {
     foreach ($tree as $data) {
       if ($data['link']['depth'] > $depth_limit) {
         // Don't iterate through any links on this level.
@@ -503,7 +499,7 @@ protected function recurseTableOfContents($tree, $indent, &$toc, $exclude, $dept
    *   An array of (menu link ID, title) pairs for use as options for selecting a
    *   book page.
    */
-  public function getTableOfContents($bid, $depth_limit, $exclude = array()) {
+  public function getTableOfContents($bid, $depth_limit, array $exclude = array()) {
     $tree = menu_tree_all_data($this->createMenuName($bid));
     $toc = array();
     $this->recurseTableOfContents($tree, '', $toc, $exclude, $depth_limit);
diff --git a/core/modules/book/lib/Drupal/book/Form/BookOutlineForm.php b/core/modules/book/lib/Drupal/book/Form/BookOutlineForm.php
index b60ef0f..549fb04 100644
--- a/core/modules/book/lib/Drupal/book/Form/BookOutlineForm.php
+++ b/core/modules/book/lib/Drupal/book/Form/BookOutlineForm.php
@@ -62,7 +62,7 @@ public function form(array $form, array &$form_state) {
 
     if (!isset($this->entity->book)) {
       // The node is not part of any book yet - set default options.
-      $this->entity->book = $this->bookManager->linkDefaults($this->entity->id());
+      $this->entity->book = $this->bookManager->getLinkDefaults($this->entity->id());
     }
     else {
       $this->entity->book['original_bid'] = $this->entity->book['bid'];
@@ -70,7 +70,7 @@ public function form(array $form, array &$form_state) {
 
     // Find the depth limit for the parent select.
     if (!isset($this->entity->book['parent_depth_limit'])) {
-      $this->entity->book['parent_depth_limit'] = $this->bookManager->parentDepthLimit($this->entity->book);
+      $this->entity->book['parent_depth_limit'] = $this->bookManager->getParentDepthLimit($this->entity->book);
     }
     $form = $this->bookManager->addFormElements($form, $form_state, $this->entity, $this->getCurrentUser());
 
@@ -84,7 +84,7 @@ protected function actions(array $form, array &$form_state) {
     $actions = parent::actions($form, $form_state);
     $actions['submit']['#value'] = $this->entity->book['original_bid'] ? $this->t('Update book outline') : $this->t('Add to book outline');
     $actions['delete']['#value'] = $this->t('Remove from book outline');
-    $actions['delete']['#access'] = $this->bookManager->nodeIsRemovable($this->entity);
+    $actions['delete']['#access'] = $this->bookManager->checkNodeIsRemovable($this->entity);
     return $actions;
   }