Kindle for iPhone is a brilliant concept, providing any Kindle user with access to all the books they've purchased for the kindle from Amazon directly from the iPhone. This is super convenient when I find myself with a spare moment on Bart or waiting for Muni. Before I'd play a game or read a blog if I had net access. Now I can read Kafka <3

The best feature is that it automatically synchronizes to the furthest page read on all your devices. There is one small problem with the feature based upon the Amazon-advised Kindle practice of shutting off the wifi whenever possible to optimize battery life. If you do this, you lose the benefit of synchronization and have to manually find your place in a book. I'll have to change my habits and plug in my Kindle more than once every 2 weeks, I suppose. I'm cool with that.