I got this book about 3 weeks ago, and so far I am really enjoying the exercises. If I understand the book correctly, you should stick with one system until you can get through all the melody charts with that system, and then move on to the next system and start with the first melody page again. Is that how you did it? I ask because I'm particularly interested in some of the system patterns more than others, because they apply more to what I want to improve in my playing (HH foot on the upbeats). Just curious if you see any harm in going out of order.