Google Book Search API

The Google Book Search Book Viewability API enables developers to:

                   

• Link to Books in Google Book Search using ISBNs, LCCNs, and OCLC numbers
• Know whether Google Book Search has a specific title and what the viewability of that title is
• Generate links to a thumbnail of the cover of a book
• Generate links to an informational page about a book
• Generate links to a preview of a book

http://code.google.com/apis/books/

via LibraryThing blog - Google Books in LibraryThing - March 13, 2008

We need APIs everywhere for everything.