While this is interesting, many readers don't want to read e-books on a small screen, or simply don't want to buy books that are not made of dead trees. However, you can use the Kindle app for something else: to get previews of just about any book an Amazon.com. (Currently, that's 245,000 books, according to Amazon.)
To do this, install the Kindle app on your iPhone or iPod touch, then set up your account. Go to the Amazon site, and find a book you're interested in. Click Send Sample Now to have a sample sent to your iPhone or iPod touch. When you open the Kindle app, sync it, and you'll get the sample. You can read a long-ish chapter of the book you're interested in -- much more than Amazon's Look Inside feature offers you.
So if you want to sample a book, use the Kindle app, then buy the book on paper; or, try an e-book to see if you like reading on your iPhone or iPod touch.

