Everyone should buy the Official Guide from ETS, it's the only source of questions from the makers of the GRE. Other than that, there's a lot of noise out there when it comes to buying GRE books, especially since the test changed in Aug. 2011 and many books were rushed to print before that date without knowing all the details of the new exam. Manhattan GRE, while on the expensive side if you buy the entire set, is a good bet.
Hope that helps!