Another aspect in qigong is microcosmic circulation. I haven't personally practiced from any books on that, but Yang Jwing Ming's Small Circulation DVD was pretty informative. I bet the book would be even more so.
And the most important thing is embryonic breathing! Yang Jwing Ming's book on that is a must have.
I have been practicing Zhan Zhuang style qigong for 2+ years. Making big stides presently. The book is called "The Way of Energy" by Master Lam Cam Chuen. Fairly easy to perform this style without an instructor or a video.
Don't be overwhelmed by the size. My advice is just go to the section on how to practice, and do natural and reverse methods. The rest is just for understanding, which is worthless in comparison to actually practicing.
Do you actually practice the Embryonic Breathing, or other QiGung Methods? Do you find that they integrate well with the AYP system? Do you do it on a daily basis like ayp practices?
Yes I practice the methods in that book, as well as others (Kunlun). I think natural breathing goes very well with every system out there...but I don't practice AYP anymore. Peace.