Our guarantee is simple. If you don't like anything you buy from us for any reason, we will refund all your money (except shipping charges) with no questions asked. No need for any explanation. Just send them back and we will credit you. You don't usually find a guarantee like that when buying books. That's because I'm very confident that if you try my materials you will find them more challenging and useful than just about anything else you have. I can honestly say that since 1994 I have only had one Sight Reading book returned because the person thought it was too difficult for him. That's pretty good. That's why you have nothing to lose.