I used both the Princeton review book and the REA book. My suggestion is:
Princeton: use both the review material (summaries) and practice problems - everything here is similar to the real test.
REA: skip the review (especially numerical analysis, statistics -- the things he talks about are way too esoteric for the actual test). However, do all 6 practice tests. Contrary to some reviews of the book online, the 6 tests are not that different in difficulty to the real tests that I encountered. The only difference is, the real test would not contain the more "involved" questions (it's clear which ones, like you said).
Arslim: the used REA book costs just 5 dollars at Amazon: http://www.amazon.com/GRE-Mathematics-R ... 0878916377