The Google Books Blog announced they have now created a mobile version of Google Books. If you have an iPhone or Android phone just navigate your mobile browser to http://books.google.com/m to start using Google Book search on your mobile device.
There are many differences between the mobile version and the regular version. The most obvious is the look and feel, but the biggest technological difference, as Google explains, is the use of OCR technology. Google Book Search typically shows scans of the page, but if you view the book on a mobile device, they will try to extract the text using OCR and show you plain text, not scanned text.
Here are some screen captures of me playing with the mobile version of Google Book Search: