Google will accept publishers of a variety of websites into the , including online retailers, blogs and book publishers.

It's common for online retailers to have affiliate programs. However, some U.S. states have recently passed laws that force e-tailers to collect sales taxes from shoppers who buy through online affiliates. In response, Amazon and Overstock have terminated their affiliate relationships with vendors in some states.

Google started doing a limited test of its program back in December.

"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," wrote Pratip Banerji, product manager at the Google Books team, .

Google's eBookstore has about 3 million free titles and hundreds of thousands for sale. Participating publishers can hook up their sites to the program's main product feed, which gives them access to all books for sale. They can also customize the pool of books available to their site by working with .