If you use these books you should also get CG's book "Brass Playing is no Harder Than Deep Breathing". It will help in understanding the methodology. Rowuk is right that this is probably not for a beginner as a self help method. I am using on a comeback, but I used it before (some 25 years ago) and have a pretty good idea how it is meant to be used.

There are sections that are really a lot of material and it is very tiring at times. I have seen lots of discussion by CG students who say that he tailored his instruction for every student. There are lessons that seem fairly easy and there are places where you are doing 3 Clarke studies that take forever. I had to cut back at certain places and use common sense in the amount of practice time to avoid overpractice. Also, READ all of the intro material by Clarke and CG in their books. Lots of good advice on how to approach the material.

It is a great method, but be careful in using it. I have to spread it across the day in order to get through the material. I can do most sections in 20 minutes or so adding up to anywhere from 45 minutes to 2 hours. Finally, it is NOT a high note method. It is comprehensive and will improve your playing. Just do some homework before you jump in with both feet.