Google Books APIs
You can take picture the barcode of a book, find information about it, that is found at and the user can read reviews from other users of the App, and even add his own review.
The current version can be downloaded here, but there are more to be done, like user login and authentication using Firebase.
https://drive.google.com/open?id=0BxHY5QjZ1t84ZXd3ZzA2Q0VkbkU