This, and all of Louise Gordon's books, are amazing, giving the reader a deep understanding of what is really going on with the foundational structure of the body beneath the skin.
I bought one of Louise Gordon's books, "The Figure in Action", early on in my art education in the early 1990's, after which I did a very rigorous set of human anatomy courses. I've done a great deal of medical illustration for the Canadian Red Cross and for Dogs in Canada Magazine (it's amazing how much human anatomy relates to the anatomy of all mammals, and amphibians and reptiles too).
Her extremely informative illustrations are beautiful to look at and masterfully rendered. The accompanying text is very clear and tailored to be most relevant to artists. She shows not just where the muscles and bones are but also how they relate to each other to move and position the body. Muscles don't just pull the bones in a straight line. They slide and wrap and shift over and around and even through each other as we move. Gordon really helped me understand this in a way that I can apply directly to my drawings of people. I highly recommend any of her books for any artist who wants to develop an intuitive mental three-dimensional movable model of the human body. This will improve your drawings of people in any context.How To Draw The Human HeadHow To Draw The Human Figure