Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Good for review, not for teaching

Book is helpful mainly as a long list of sample questions and answers. Doesn't provide much teaching of what you need to know in certain sections (eg the math section doesn't cover some of the more complex rules of geometry etc that you need to answer the questions). Advice on how to take the test is pretty basic too. I would say this is a good book if you are reasonably confident that you will do well and it really is just a review book to remind you of a few things you may have forgotten; the answers are clear and well written, and so are helpful for 'brushing up' on what you may have forgotten, although at least one is wrong (or not fully right), and there are quite a few typos, but if you know your stuff this won't really through you off (beyond the fear that there could be mistakes on the GMAT itself!)