BookMooch is a community for exchanging used books. BookMooch lets you give away books you no longer need in exchange for books you really want. All the API calls support XML output, by adding &o=xml on the GET url line.
Additional book-related API's:

ISBNdb API

O'Reilly Safari API

Provider: BookMooch	Submitted By: APIFinder.com Staff
License: Open (free)	Email: Email this contributor
Price: 0	Connection Protocols: REST
Notes: No more than 10 API calls per second.
Functions: Other Function
Languages/OS: Web Service