diff --git a/src/index.d.ts b/src/index.d.ts
index d3939ea..39fbcf6 100644
--- a/src/index.d.ts
+++ b/src/index.d.ts
@@ -7,7 +7,7 @@
  * @property {number} pageCount - The number of pages in the book.
  * @property {string} printType - The print type of the book. Always "BOOK" for this context.
  * @property {string[]} categories - The subjects or categories of the book.
- * @property {string} thumbnail - The thumbnail image link of the book.
+ * @property {string | undefined} [thumbnail] - The thumbnail image link of the book.
  * @property {string} [link] - The link of the book.
  */
 /**
@@ -73,7 +73,7 @@ export type Book = {
     /**
      * - The thumbnail image link of the book.
      */
-    thumbnail: string;
+    thumbnail?: string | undefined;
     /**
      * - The link of the book.
      */
diff --git a/src/index.js b/src/index.js
index f0d6ef7..8456f41 100644
--- a/src/index.js
+++ b/src/index.js
@@ -13,7 +13,7 @@ import {
  * @property {number} pageCount - The number of pages in the book.
  * @property {string} printType - The print type of the book. Always "BOOK" for this context.
  * @property {string[]} categories - The subjects or categories of the book.
- * @property {string} thumbnail - The thumbnail image link of the book.
+ * @property {string | undefined} [thumbnail] - The thumbnail image link of the book.
  * @property {string} [link] - The link of the book.
  */
 
diff --git a/src/providers/google.js b/src/providers/google.js
index 1beff43..8544331 100644
--- a/src/providers/google.js
+++ b/src/providers/google.js
@@ -38,12 +38,22 @@ export async function resolveGoogle(isbn, options) {
       throw new Error(`No volume info found for book with isbn: ${isbn}`);
     }
     const book = books.items[0];
-    return standardize(book.volumeInfo, book.id, isbn);
+    return standardize(book.volumeInfo, isbn);
   } catch (error) {
     throw new Error(error.message);
   }
 }
 
+/**
+ * @typedef {object} ImageLinks
+ * @property {string} [extraLarge] - extraLarge
+ * @property {string} [large] - large
+ * @property {string} [medium] - medium
+ * @property {string} [small] - small
+ * @property {string} [thumbnail] - thumbnail
+ * @property {string} [smallThumbnail] - smallThumbnail
+ */
+
 /**
  * @typedef {object} GoogleBook
  * @property {string} title - The title of the book.
@@ -63,7 +73,7 @@ export async function resolveGoogle(isbn, options) {
  * @property {boolean} allowAnonLogging - The allow anon logging of the book.
  * @property {string} contentVersion - The content version of the book.
  * @property {object} panelizationSummary - The panelization summary of the book.
- * @property {object} imageLinks - The image links of the book.
+ * @property {ImageLinks} [imageLinks] - The image links of the book.
  * @property {string} language - The language of the book.
  * @property {string} previewLink - The preview link of the book.
  * @property {string} infoLink - The info link of the book.
@@ -76,11 +86,10 @@ export async function resolveGoogle(isbn, options) {
 /**
  * Standardizes a book object by extracting relevant information from the provided book object.
  * @param {GoogleBook} book - The book object to be standardized.
- * @param {string} id - The book's id.
  * @param {string} isbn - The book's ISBN.
- * @returns {Book} - The standardized book object.
+ * @returns {Book} The standardized book object.
  */
-export function standardize(book, id, isbn) {
+export function standardize(book, isbn) {
   const standardBook = {
     title: book.title,
     authors: book.authors,
@@ -88,10 +97,35 @@ export function standardize(book, id, isbn) {
     pageCount: book.pageCount,
     printType: book.printType,
     categories: book.categories,
-    thumbnail: `https://books.google.com/books?id=${id}&printsec=frontcover&img=1&zoom=6&edge=curl&source=gbs_api`,
+    thumbnail: getLargestThumbnail(book.imageLinks),
     link: book.canonicalVolumeLink,
     isbn,
   };
 
   return standardBook;
 }
+
+/**
+ * Get the largest available thumbnail from a book's image links.
+ * @param {ImageLinks} [imageLinks] - The image links object.
+ * @returns {string|undefined} The URL of the largest thumbnail, or undefined if not found.
+ */
+function getLargestThumbnail(imageLinks) {
+  const sizes = [
+    "extraLarge",
+    "large",
+    "medium",
+    "small",
+    "thumbnail",
+    "smallThumbnail",
+  ];
+
+  if (!imageLinks) return;
+
+  for (const size of sizes) {
+    if (size in imageLinks) {
+      // @ts-ignore
+      return imageLinks[size];
+    }
+  }
+}
diff --git a/test/end-to-end.test.js b/test/end-to-end.test.js
index be3a873..78ed781 100644
--- a/test/end-to-end.test.js
+++ b/test/end-to-end.test.js
@@ -24,7 +24,7 @@ describe("End to end", () => {
         "link": "https://books.google.com/books/about/Annihilation.html?hl=&id=2cl7AgAAQBAJ",
         "pageCount": 209,
         "printType": "BOOK",
-        "thumbnail": "https://books.google.com/books?id=2cl7AgAAQBAJ&printsec=frontcover&img=1&zoom=6&edge=curl&source=gbs_api",
+        "thumbnail": "http://books.google.com/books/content?id=2cl7AgAAQBAJ&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api",
         "title": "Annihilation",
       }
     `);
@@ -107,7 +107,7 @@ describe("End to end", () => {
         "link": "https://books.google.com/books/about/Annihilation.html?hl=&id=2cl7AgAAQBAJ",
         "pageCount": 209,
         "printType": "BOOK",
-        "thumbnail": "https://books.google.com/books?id=2cl7AgAAQBAJ&printsec=frontcover&img=1&zoom=6&edge=curl&source=gbs_api",
+        "thumbnail": "http://books.google.com/books/content?id=2cl7AgAAQBAJ&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api",
         "title": "Annihilation",
       }
     `);
diff --git a/test/index.test.js b/test/index.test.js
index 919db53..0ccbaf5 100644
--- a/test/index.test.js
+++ b/test/index.test.js
@@ -48,7 +48,7 @@ describe("ISBN Resolver API", () => {
           "link": "https://books.google.com/books/about/Annihilation.html?hl=&id=2cl7AgAAQBAJ",
           "pageCount": 209,
           "printType": "BOOK",
-          "thumbnail": "https://books.google.com/books?id=2cl7AgAAQBAJ&printsec=frontcover&img=1&zoom=6&edge=curl&source=gbs_api",
+          "thumbnail": "http://books.google.com/books/content?id=2cl7AgAAQBAJ&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api",
           "title": "Annihilation",
         }
       `);
@@ -236,7 +236,7 @@ describe("ISBN Resolver API", () => {
           "link": "https://books.google.com/books/about/Annihilation.html?hl=&id=2cl7AgAAQBAJ",
           "pageCount": 209,
           "printType": "BOOK",
-          "thumbnail": "https://books.google.com/books?id=2cl7AgAAQBAJ&printsec=frontcover&img=1&zoom=6&edge=curl&source=gbs_api",
+          "thumbnail": "http://books.google.com/books/content?id=2cl7AgAAQBAJ&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api",
           "title": "Annihilation",
         }
       `);
@@ -268,7 +268,7 @@ describe("ISBN Resolver API", () => {
           "link": "https://books.google.com/books/about/Annihilation.html?hl=&id=2cl7AgAAQBAJ",
           "pageCount": 209,
           "printType": "BOOK",
-          "thumbnail": "https://books.google.com/books?id=2cl7AgAAQBAJ&printsec=frontcover&img=1&zoom=6&edge=curl&source=gbs_api",
+          "thumbnail": "http://books.google.com/books/content?id=2cl7AgAAQBAJ&printsec=frontcover&img=1&zoom=1&edge=curl&source=gbs_api",
           "title": "Annihilation",
         }
       `);
diff --git a/test/providers/google.test.js b/test/providers/google.test.js
index bc534d8..0d1dada 100644
--- a/test/providers/google.test.js
+++ b/test/providers/google.test.js
@@ -28,20 +28,20 @@ describe("resolveGoogle", () => {
 
     const book = await resolveGoogle(isbn, {});
     expect(book).toMatchInlineSnapshot(`
-{
-  "authors": [
-    "Test Author",
-  ],
-  "categories": undefined,
-  "description": undefined,
-  "isbn": "1234567890",
-  "link": undefined,
-  "pageCount": undefined,
-  "printType": undefined,
-  "thumbnail": "https://books.google.com/books?id=11223344000&printsec=frontcover&img=1&zoom=6&edge=curl&source=gbs_api",
-  "title": "Test Book",
-}
-`);
+      {
+        "authors": [
+          "Test Author",
+        ],
+        "categories": undefined,
+        "description": undefined,
+        "isbn": "1234567890",
+        "link": undefined,
+        "pageCount": undefined,
+        "printType": undefined,
+        "thumbnail": undefined,
+        "title": "Test Book",
+      }
+    `);
   });
 
   it("should throw an error if no books are found", async () => {
@@ -55,7 +55,7 @@ describe("resolveGoogle", () => {
     });
 
     await expect(resolveGoogle(isbn, {})).rejects.toThrow(
-      `No books found with isbn: ${isbn}`,
+      `No books found with isbn: ${isbn}`
     );
   });
 
@@ -71,7 +71,7 @@ describe("resolveGoogle", () => {
     });
 
     await expect(resolveGoogle(isbn, {})).rejects.toThrow(
-      `Wrong response code: 404`,
+      `Wrong response code: 404`
     );
   });
 
@@ -87,7 +87,7 @@ describe("resolveGoogle", () => {
     });
 
     await expect(resolveGoogle(isbn, {})).rejects.toThrow(
-      `No volume info found for book with isbn: ${isbn}`,
+      `No volume info found for book with isbn: ${isbn}`
     );
   });
 });
diff --git a/tsconfig.json b/tsconfig.json
index 115ef6b..4e1b0e4 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -12,6 +12,6 @@
     "target": "es2022",
     "useUnknownInCatchVariables": false
   },
-  "include": ["src/*.js"],
-  "exclude": ["src/*.d.ts"]
+  "include": ["src/**/*.js"],
+  "exclude": ["**/*.d.ts"]
 }