致命错误：Google电子书的未捕获异常'Google_Service_Exception'

在PHP中，我试图通过谷歌api访问谷歌电子书但我收到此错误 .

致命错误：未捕获的异常 'Google_Service_Exception' 与消息“错误调用GET https://www.googleapis.com/books/v1/volumes?q=Henry梭罗＆滤波器=自由电子书＆键= AIzaSyCc5s6WLKl9SrvlsN-8yXO6Cmd4qeAYR08：（403）的权限不足'in /home/stealthbeta/public_html/google-api-php-client-master/src/Google/Http/REST.php:110堆栈追踪：＃0 / home / stealthbeta / public_html / google-api-php-client-主/ SRC /谷歌/ HTTP / REST.php（62）：Google_Http_REST :: decodeHttpResponse（对象（Google_Http_Request），对象（Google_Client））＃1 [内部功能]：Google_Http_REST :: doExecute（对象（Google_Client），对象（Google_Http_Request ））＃2 /home/stealthbeta/public_html/google-api-php-client-master/src/Google/Task/Runner.php(174）：call_user_func_array（阵列，阵列）＃3 /家庭/ stealthbeta /的public_html /谷歌-api-php-client-master / src / Google / Http / REST.php（46）：Google_Task_Runner-> run（）＃4 / home / stealthbeta / public_html / google-api-php-client-master / src / Google /Client.php(593）：Google_Http_REST :: e xecute（对象（Google_Client），对象（转到第110行的/home/stealthbeta/public_html/google-api-php-client-master/src/Google/Http/REST.php

这是我的代码：

require_once 'src/Google/autoload.php';
require_once 'src/Google/Client.php';
session_start();
$client = new Google_Client();
$client->setApplicationName("XXXXXX");
$client->setClientId("XXXXXXX");
$client->setClientSecret('XXXXX');
$client->setRedirectUri('XXXXX');
$client->setScopes(array('https://www.googleapis.com/auth/books'));

if (isset($_GET['code'])) {
    $client->authenticate($_GET['code']);
    $_SESSION['token'] = $client->getAccessToken();

    if (isset($_SESSION['token'])) {
        $client->setAccessToken($_SESSION['token']);
     }
}

if ($client->getAccessToken()) {
    $service = new Google_Service_Books($client);
    $optParams = array('filter' => 'free-ebooks');
    $results = $service->volumes->listVolumes('Henry David Thoreau', $optParams);

    foreach ($results as $item) {
        echo $item['volumeInfo']['title'], "
 \n";
    }

    $_SESSION['token'] = $client->getAccessToken();
} else {
    $authUrl = $client->createAuthUrl();
}

如何解决这个问题？