I bought the Gruber books , SAT 2400,and Gruber's Complete Sat Math Workbook to help my student increase his scores in general , and specifically in his.weak area- Math. His score in Math was 450 which he got on the March Sat. He studied this book by taking the diagnostic tests and reading the instructional material. As advised in the book. He went through the clearcut strategies and shortcuts, and then took the practice tests at the end of the book. To make a long story short, his math scores increased by 240 points! We were thrilled when he got a 690. He also got Gruber's 2400 SAT book to increase his scores in the other areas and he is learning even more strategies for his final test and we are expecting scores in the 2100 range , as Reading and Writing are already strong subjects for him. Obviously the Gruber approach accounts for the substantial increase in an SAT score. One reviewer of this Math book scoffs at the idea that scores went up 600 pts. Gruber in his own words clearly says that 600 points, is for math,, reading and writing combined! A preparation book for the Sat's should train the student to solve similar problems on the test and even harder problems than what will be asked on the test. That is exactly what the book does, so my student reported sailing through the test with much greater ease and confidence. I believe that the Gruber book is a great advantage and that any parent or caring teacher would be well advised to purchase it. It is a small price to pay for a higher score, a better school and potentially easier and more successful life.