I have tried kaplan and other brands to help increase my GRE math score but I found this book by far to be the best. Some of the questions are indeed harder than what you will see on the test which is a good thing as I stuied from this book for 4 weeks and my quantitave score improved drastically. After the 4 weeks I returned to look at some questions in other math prep books such as Kaplan and I could do them all, even the difficult ones quiet easily. You need to be meticulous about studying the questions and if you dont know where an answer comes from, persist with it until you do - the book does not always explain answers in the best way but I feel this is an advantage as you have to root out the solutions yourself which is the best way to learn.

You need a good understanding of math concepts and this book is not for beginners. It will definitely get you into the 700-800 bracket quiet easily. Acknowledged there are mistakes here and there in the book but the way I look at it is if you can find them and know that the mistakes are there then you are doing good!