mathmom, the local high school had plenty of summer work for AP classes, but reading a review book was never one of them. I think it might have made the students drop the course like flies, if it had been. 
I think American history is fascinating, but quick dips into several review books left me mostly bored to tears (except in one case where I wondered whether the sample essay had really been written by a high school student in an AP class, or by someone who was considerably further along).