global $wpdb;
$createSQL              =   "
CREATE TABLE `". $wpdb->prefix ."_book_ratings` (
  `id` bigint(20) UNSIGNED NOT NULL AUTO_INCREMENT,
  `book_id` bigint(20) UNSIGNED NOT NULL,
  `rating` float(3.1) UNSIGNED NOT NULL,
  `user_ip` varchar(32) NOT NULL
) ENGINE=InnoDB" . $wpdb->get_charset_collate() . " AUTO_INCREMENT=1;
";

require( ABSPATH . '/wp-admin/includes/upgrade.php' );
dbDelta( $createSQL );