I have used it and it worked for me. What you will find is, that it takes a while to get to your advantage. Once there I have found it very effective. That being said if you follow the authors instruction you will get a lot of attention going from your small to large bet.
KO Rookie is a valid system, but consider ReKO. It's almost as simple as KO Rookie and almost as powerful as KO preferred. You just have to remember one index number.