I paid the almost $50 bucks to get Jake's Method. It is a very good, practical trumpet book offering basic and elementary advice for trumpet players. Advanced and pro trumpet players should already know everything in this book including the breathing and air section. Trumpet players in the beginning and intermediate stages plus comeback trumpet players will likely get more out of this book than Professional trumpet players.
His book is a good all-arounder and I recommend it. If you are an advanced or pro player looking to increase your high notes, this is not the book for you.