I agree with nkand and some others on here. Purchase both, or at least borrow one set and buy the others. BT comes up short in a few areas however the ATC books go in far to deep for someone at the start of learning, particularly anyone self studying.. I found if I couldn't grasp it , I'd have a look at BT's book and it would be explained much simpler. Then when I got a grasp on it I'd go back to ATC books and it would all make more sense and you can broaden your knowledge on the subject from there..