Google has launched a mobile version of its book search for iPhone and Android devices. Browse to books.google.com/m to check it out. iPhone users note that you can't simply browse to the regular books.google.com site and expect to be sent to the mobile site. Some web developers have included device detection in their sites, but not this one.
Here's what some of the pages will look like once you browse to Book Search on the Android (left) and iPhone (right):