There's been a few threads about this, and I'm on the fence. I'm liking the minimalistic features of iOS 7. But does iBooks really need to be updated?
Newsstand is awful in my opinion. (And the fact that you can't pinch to come out of it is annoying too).
So maybe keeping iBooks as it is inside the app, and updating it's logo to fit the feel of the rest of the OS. Because right now, iBooks isn't on my 1st page because it just doesn't fit.
Apple created a company where it's users expect nothing but perfect, so whatever update they make I suppose we'll moan until it is.