Improve Jumping

My son wants to improve his hops, he is 14 5'7", what do you think about the Jump Manuel that is all over the internet?

This is the first time I have heard of this.... I listened to his pitch... and it sounds good, but I cant for one say that it is or is not any good...... you will have to make the decision...... you can get a free trial so whats to lose?

http://jumpmanual.com/