I can't imagine the reviews online being much different than the book reviews (in terms of content), but that begs the question as to why the online review is so much more expensive. I'm not sure, I don't have much experience with Kaplan.
Either way, depending on how much time you have left, you might want to check out TBR for chemistry, since it seems to be a consensus around here that they have the best gen chem review. The books might take a while to get to you, and they are kind of big, so it may not be worth it if you are just looking for a quick clarification.