Ebook: Force: Dynamic Life Drawing for Animators, Second Edition

I don't know about Mr. Mattesi's theory on drawing movement: it looks a bit too esoteric and obscure, and after a while I just stopped reading it, but his drawings are really really good and I learned a lot just observing them. I recommend this book because if you're interested in drawing human body in movement there are lots of tricks and techniques: it may improve your drawings.