They seem to be the most hardcore prep books out there. So much so that it seems like an exaggeration They are also much more expensive. Is it worth it?
I used the free Ivy Global tests that you can download on http://ssatprep.com/free-practice/. I also used Princeton Review, which is no more than $20. Both were helpful, and I scored well. Maybe you could try using Princeton Review to get explanations and Ivy Global, which has the most realistic tests, to see how you would do. Good luck!