Good review of basic concepts and has some cool shortcuts too. I wouldn't recommend these until you know the regular ways backwards and forwards.
I do think the pretest was easier than the post test though. Also the lottery ticket question of the pretest was unclear about if the winning ticket outcomes are independent or not.
This book has been very helpful when studying for the GRE. Although the name is a misnomer. There were plenty of times where the lessons took well over an hour. Overall I thought the book was a thorough glance into basic arithmetic. My one complaint is that there are a few answers that I knew where wrong in the book. It lead me to wonder if there were more that I didn't know where wrong.
I hate math, so I only read this because I am so terrible at it that I knew there was no way I'd be able to pass the GMAT without first boning up on the basics. For a math book, it was ok. I have to admit it was helpful, and I'm glad I got it.