Instruct: Classify Amazon reviews into positive or negative sentiment
Query: It is just waste of $$$!

This book is not helpful at all. The definitions of some vocabularies are not exact, they can give some sort of confusion to the test takers. Even though this book provides some good groups of similar vocabularies, it is not that useful also because modern tendency of GRE is asking more the exact meaning of a vocabulary. It would be better to study the detail and exact definitions of vocabularies through some good dictionaries.