At the moment while you can buy print books via that app you can’t buy Kindle versions. I wonder if they will modify that app to allow you to do that now that you can have Kindle books on the iPhone/Touch?

There is no in-app capacity for purchasing books. This may be due to a stipulation in Apple’s iPhone Developer agreement, which says that programs cannot provide additional content through distribution methods other than the iTunes Store without prior written consent from Apple. Most other e-book readers for the iPhone that offer the option of purchasing books, like Stanza or eReader, get around this by routing users to an e-book store via an embedded WebKit view. So far, this approach hasn’t been rejected by Apple.

And to be honest, although I haven’t tried the Kindle app yet, I prefer eReader to Stanza largely BECAUSE I prefer the swipe page turn to the tap. When I use Stanza I have to set the left tap zone to be my forward page turn because having to break my view of the page to tap the right side interrupts my reading. Personal preference.