A must have from Apple. Besides use it to read books you buy from iTune store, you can also add your own books (like PDFs) through iTune.
The animation of flipping pages is amazing.
Don't forget to get the free text book: Life on Earth (1G in size).
You can rotate the DNS models using your finger in the book!
What I don't like is it takes a while to start this app. I don't know what Apple is doing during this time.