bookinventory/app/Services/BookInformation/GoogleBooks.php

<?php

namespace App\Services\BookInformation;

use Google_Client;
use Google_Service_Books;
use Illuminate\Support\Arr;

class GoogleBooks implements BookLookupService {

    public function lookup($isbn) {
        $client = new Google_Client();
        $client->setApplicationName("BookInventory");
        $client->setDeveloperKey(env('GOOGLE_BOOKS_KEY'));

        $service = new Google_Service_Books($client);

        $results = $service->volumes->listVolumes('isbn:' . $isbn);

        /**
         * @var \Google_Service_Books_Volume
         */
        $volume = Arr::first($results->getItems())->getVolumeInfo();

        return [
            'title' => $volume->getTitle(),
            'authors' => $volume->getAuthors()
        ];
    }
}