I bought it, it helped, but remember it is an E-Book!
Don't think that his book will get you into dental school, it is a guide, it is not the secret key that unlocks the doors.
If you read it carefully you should get some knowledge out of it. Besides it is your future don't be super cheap! If you think that those $40 bucks are too much money, just wait until you start getting interviews, then you will see that those $40 are minimal. I also bought some of the books on ADEA website, gather as much info as you can when you are preparing to apply.
Buy it, it won't hurt.