i bought the book on amazon the week after it came out. it was perfect timing for me as i had already scheduled to retake the test and was focusing almost exclusively on improving my quant.
the book does a really good on teaching you alternative methods for solving 70 percentile level and above problems (~Q46). once you get to the 80+ percentile problems, they begin to test your ability to recognize certain details and subtleties. Things like the product of 3 consecutive numbers is always divisible by 3. this book does a good job at going through some of these with specific strategies and tactics. they even start to go into guessing techniques when you get stuck on certain types of problems. for example, in probability problems, find answer pairs. if one answer is 2/3 and another is 1/3, guessing one of these two is better than guessing randomly. things like that.
note. it does not go through any math principals. it assumes you have a solid grasp of all the material from the regular
mgmat quant books (which are excellent and i recommend). basically, it assumes you are consistently scoring at least Q45. if you are not, i would recommend reviewing the regular
mgmat quant books again rather than picking up this book.
also note that there are a few mistakes, typos, and missing pictures which can be a little confusing. its a 1st edition.
i already took my test and it's been over a month since i read the book so i don't remember too much more detail to make this a more detailed review. but i can tell you that my official test score in quant went from a Q46 before this book to a Q49 after this book. i can't confidently say it was only because of this. in fact, i also used gmatclub practice tests (i also recommend these), but my score improved and i'm sure this book was at least part of the reason why.
in summary, it's a great book if you're stuck around the Q45-47 range and have already gone through all the official problems. I would recommend this book as the last step in your quant study. use it after all the regular
mgmat quant books and after all the official guide problems. not before and definitely not instead of. the book has good tips and a lot of practice problems with solutions to break the 80% ceiling.
good luck!