Books.app is a simple eBook reader for the iPhone. It reads HTML and text files stored in your Media/EBooks folder, and is smart enough to enter subdirectories, if, for instance, you’ve broken a book down by chapters.

In addition, at least one bug ( issue #13 ) has been fixed by the 1.1.1 update, or so it appears. Thanks, Apple! 🙂

http://code.google.com/p/iphoneebooks/