book_node_predelete

book_node_predelete(EntityInterface $node)

function book_node_predelete(EntityInterface $node) {
  if (!empty($node->book['bid'])) {
    /** @var \Drupal\book\BookManagerInterface $book_manager */
    $book_manager = \Drupal::service('book.manager');
    $book_manager->deleteFromBook($node->book['nid']);
  }
}