[authors_summary] => Array
        (
            [0] => Array
                (
                    [id] => 123456789
                    [name] => Ben Smith
                )

            [1] => Array
                (
                    [nconst] => 987654321
                    [name] => Tommy Lee
                )

        )

$authors = $book->authors_summary[0]['name'];

$authors = $book->authors_summary[0]['name'];
echo $authors;

)