The search on ibooks is horrible, if you type WW2 it won't find any World War 2, WWII or World War 2 or two books
... I agree about the more books than you could ever read statement, but if you want a nice reference library you can carry with you on a subject you like, then kindle app/ibooks/ipad is pretty good. I have nothing but WW2 Aviation stuff on mine.
There's lots of books on guns too
