Inside Google Books: New Books API for Developers

"Today, we [Google] are releasing a new Google Books API in Code Labs. The new Books API will help you write applications to query for the more than 15 million books that are searchable on books.google.com including book metadata, pricing and more. This API replaces the Google Book Search Data and Javascript APIs. The previous GData API and Javascript API will still be available, but ongoing development work will be focused on the new Google Books API so we encourage you to make the transition to take advantage of new features....