$book_args= array('post_type' => 'books',
              'post_type_singular'  => 'book',
              'fields'              => array(
                                        'ISBN' => 'text'
                                        ),
              'fields_list'         => array(
                                        'ISBN' => 'text'
                                        ),
              'taxonomies'          => array('category', 'tag')
              );
$book_type = new SimpulSections($book_args);