Books don't take much space. I use the kindle app (I have a kindle, too but I actually find that I read on my iphone more than I do on my kindle!) and right now I've got 8 full sized books on it (and 12 more archived that I can access if I have wifi or 3G available) and it takes up almost zero room. I've got 11GB of free space, so after you pull out all my apps and music and stuff, the books can't account for much.

I was also shocked at how quickly books download from the archives. Even using 3G, they only take a few seconds!

My only complaint about the phone is not really a complaint about the phone at all. I hate that I cannot see it without my reading glasses (any of it...not just the books). That part is a pain. I need bifocals.