If the app doesn't include the illustrations, it would lose a lot of value over the book. I think I would prefer printed anyway. I keep the book at home for study/review (makes great bathroom reading!) And I have the smaller pocket guide version tucked away in my hiking pack.

Saying "I'm cheap" and then talking about your iPhone is quite a contradiction. Those iPhones are not exactly bargain-bin priced. My son has one and I have to admit it's pretty neat. But I couldn't afford one (CHOOSE not to afford one) for myself though.