From the Inside Google Books Blog:
Retailers, bloggers, book publishers and other website owners in the U.S. can now become Google eBooks affiliates. Affiliates can link to Google eBooks on their sites for any of the hundreds of thousands of titles available for sale, earning a commission for referring sales to the Google eBookstore.
We launched the program as a limited beta in December with our first affiliate, Goodreads. Goodreads is a social reading site, who after becoming an affiliate was able to refer their avid book reading fans to the Google eBookstore. When Goodreads users buy a Google eBook, they’re gaining immediate access to their book and supporting Goodreads in the process.
Starting today, we invite all interested site owners to apply to join the expanded Google eBooks affiliate program. Participating sites gain new revenue streams by giving their book-reading audiences an easy way to buy Google eBooks.
Google eBooks affiliates become part of the Google Affiliate Network (GAN). After joining GAN, you can subscribe to the Google eBooks product feed to get links to the full set of available Google eBooks. If you want to query a more targeted set of ebooks you can use the new Google Books APIs.
For more information and to sign up to be a Google eBooks affiliate, please visit our partner Help Center here.