As many other reviewers have noted, this is the only book on the market that is produced by ETS, the company that writes and administers the GRE; however, please know that this does not mean that buying this book is a no-brainer. Far from it. The book may be helpful to you in some respects, but I would never recommend purchasing only it to study for the GRE. I would buy it perhaps as a supplement to a book published by a third-party (like Barron's, the Princeton Review, Kaplan, etc) or not at all. These third party books really are likely to serve you FAR better, as I will try to explain. Here are the things I think you should consider as you decide whether to purchase this book:

1) The majority of the practice questions in this book are available for FREE on the ETS website. Just check out their "Prepare for the GRE" page for pdfs.

2) The POWERPREP II software (including two practice tests) which is contained on the disc accompanying this book is also available for FREE on the ETS website. Just check out their "Prepare for the GRE" page for a download.

3) Whether you go with the book or get it online, the POWERPREP II software is Windows/IE-compatible only. (Ridiculous.)

4) The Math Review section of this book is also available for FREE on the ETS website. Just check out their "Prepare for the GRE" page for a download.

5) Many of the other explanations and general tips contained in the book are also included in the free online materials (I think it's called the Practice Book) on the ETS website.

6) All that said, if you prefer to work on paper rather than on a PDF, and you don't want to print out a giant stack of pages, you may like the idea of having ETS' materials nicely printed and bound as they are in this book.

7) One nice thing about the fact that this book was written by ETS is that you get actual old GRE questions. ETS doesn't license its old questions, so all other books will have questions meant to closely approximate authentic GRE questions, but which never actually appeared on a GRE exam. However, since you can get most of these ETS-authentic practice questions for free, as I've explained, you still may not want to spend on this book. Plus, the questions that third-parties write are, for the most part, similar enough to real GRE questions to still be very good practice.

8) The down side (and I think you should think about this carefully) to this being written by ETS is that it, naturally, sells the "ETS-Kool-Aid" - HARD. What I mean is that other third-parties will shoot you straight because they are not invested in promoting the mystique of this exam. They will tell you, for example, the true fact that the GRE really measures your ability to do well on the GRE, whereas ETS' book will claim, as ETS of course must, that the GRE is predictive of your success in graduate school. In addition, third-party books will level with you about how the GRE is written and how it is graded and will teach you tips, tricks, techniques, and work-arounds for the GRE. ETS has to take itself and its exam very, very seriously, which is likely to just scare you and stress you out. Third-parties will level with you. (See also the next point.)

9) (This is to some degree an extension of the previous point.) The Math Review that the ETS has written (recall it is also available for free online) is very misleading in some ways. Firstly, it can be confusingly-presented for those dusting off old, unused math skills. Third-party prep books will serve you far better in explaining these concepts simply, although if you need help with very basic concepts (like long division), you may want to supplement with something like Princeton Review's Math Smart I (or maybe check out tutorials online if you want to save money). Secondly, there are some math topics covered by ETS in their materials that you are simply very unlikely to see on the actual GRE; seeing them in this book will just make you anxious. You do not need to master all the math ETS gives you in this book in order to get a great score on the math portion of the GRE (after all, you can still score in the 99th percentile of test-takers even if you get a few questions wrong on the test). ETS will make it sound like you must know inside and out all the math they give you in this book, but third-party books will be much more honest with you about which concepts you actually need to master, what short-hand tips and tricks you can use, what things you may just want to memorize outright, and what minimum understandings you can totally get by with on some of the trickier math topics that might come up on the GRE.

10) Only third-party books give you actual lists of vocab words that are the most likely to appear on the GRE. This book does not. These lists are very useful in studying for the GRE.

Final thoughts:

No book will guarantee you an awesome score on an exam. The truth, in my opinion, is that major third-party prep books are probably roughly equivalent in getting you familiar with, giving you good tips for, and getting you some practice on GRE questions. You have enough to worry about without stressing over which book to choose! Just pick up one of the major third-party books and let it be your primary study guide. Get this book, if at all, only as a supplement. Do not make it your primary material for your preparation.