I liked the book - it is positioned as a Math Course, but I'd say it is a bit too intense. It jumps right away into pretty high level and dense material, so the best use for this book if you are aiming for a high quant score and willing to sweat for it. If you are just starting out, I'd probably suggest to start with Kaplan Math workbook and then grab this book (Kaplan seemed to have been laid out a bit better, but definitely not as detailed and did not include much of probability, combinations, statistics questions).
THE GOOD:
* Probably one of the most thorough GMAT quant books though sometimes a tad over the top
* Has good coverage of exotic question types: probability, statistics, combinations, fuctnions, counting, etc
* Questions arranged in Easy, Medium, Hard sections - you can skip right away to the harder questions or vice versa
* Some strategy elements
* Diagnostic test in the book
* Data sufficiency practice (about 100 questions)
* Tons of practice questions and a fair share of hard ones
THE BAD:
* Not a book for beginners and assumes familiarity with basic strategies and format of the test; has a potential to frustrate a person who is just getting into it
* 500+ pages - easy to get bogged down and can take quite a while to cover
* Does not point out which items are critical/most important to remember
* Structured in a slightly unorthodox fashion (pretty much starts with symbol-type questions and then jumps to Geometry)
* Does not help spot some of the easier solutions, but instead does a head-on approach (which is probably more reliable, but takes time)
* Has a few sections that may not be very important for the GMAT such as Graphs and Charts
Overall, good 500+ page math book and if nothing else, is a good collection of questions.
Let me know if you have any questions about this book,
BB, GMAT 750
Founder of GMAT Club