Google has launched a mobile version of Google Book Search, opening up over 1.5 million mobile public domain books in the US (and over half a million outside the US) for you to browse while buying your postage on iPhone and Android devices. Just go to books.google.com/m in your mobile browser. You can search for a title, author, or subject. Or you can browse the list of "Featured books" and various categories like business and economics, the classics, science and math, travel, and more. Once you've picked out a book or two, you can easily get back to your selections by clicking on the "Recently viewed books" under the "My books" section.
Is it Google’s Kindle?
More info: Google Book Search blog