Google is selling books online for its partners, according to its Book Search beta page:
"The Google Books Partner Program is developing tools for publishers to experiment with new and innovative ways to increase book revenue. The first of these tools allows you to sell online access to your book. Once you set a price for your book, users who discover it through Google Book Search will be able to pay for access to its full contents. The book will only be available to the user once they've signed in with their personal account, and will only be available through their browser. Users will not be able to save a copy on their computer nor copy pages from the book."
Google says that soon, it will let users pay for immediate access to books right from the browser. At first glance, it seems the company is getting into online retail.
Here's Publishers Weekly's take on it.