Instruct: Classify Amazon reviews into positive or negative sentiment
Query: This is the only useful GRE study book.

If you are going to take the GRE, buy this book and no other. The author fills you in on all the tricks you need to know to score well on the GRE (and there are many), and does not waste your time with lists of 30,000 vocabulary words. Spend your time learning the structure of the test and how to avoid the traps, then learn the basic information. Her chapters on algebra and geometry are much more useful than Barron's or any other books I looked at, and her strategy for vocabulary makes much better use of your time than memorizing vocabulary. The only way the book falls short is in preparation for the unique features of the computer-based test. All the books I looked at fell short this way, even the ones that claimed to have sections on the computer-based test.