Update 21 July 2011: It appears that Google Books is not going to be the only partner for U.S. ebook sales, but rather one partner among others. Original post follows.
A new blog post from Google today says that the company will be handling J.K. Rowling’s Pottermore.com ebook sales for U.S. customers, and that Google Checkout will be promoted (worldwide?) as the primary way to pay for things on the site:
“Also under this agreement, Google Checkout will be the preferred third party payment platform for all purchases made on Pottermore.com. When you visit the Pottermore Shop, you’ll be able to pay for your purchases using Google Checkout, in addition to using a debit or credit card.”
I’m still a little puzzled about how Pottermore + Google Books will provide DRM-free Harry Potter books that can work on the Kindle platform, because I’ve only ever seen .epub or .pdf files available for download from the Google eBookstore.