The book is definitely useful and A. Ryder is highly skilled draughstman.
However, we should never forget the fact that the highly developed skills are just the tool, not an aim in itself, lest we become what Harold Speed call "a mechanical instrument" and "unimpassioned renderers of appearance of things".
The faculty of accurate observation and good eye-hand coordination is just a
prerequisite for making art. Once a student masters that, he/she is ready to embark upon their own unique and exciting artistic journey.
As I said, A.R. is skilled draughtsman, but, I for one prefer the likes of Alvin Gittins, William Whitaker, Victor Ambrus or Robert Liberace.
Robert Beverly Hale's
Drawing Lessons from the Great Masters is a great tutorial book on drawing. Admittedly, it will not teach one how to draw, but it will help enhance one's perceptivness, which is of utmost importance in visual arts.
(Oh, I almost forgot: I can not understand why A.R. circumscribe his figures ??? My teacher at the Academy called such a line (that of uniform thickness around the figure or a cast) "a wire". We learned very early basics like - thick in shadows and thin where light fall upon the form, etc.. Another thing: shadows contribute in expressioning the sense of bulk - that is, the third dimension. Shadows on a human form should not be flat. It is obvious that A.R. knows how to create an illusion of solidity of the form, so it was even more disturbing for me to see those large flat shadow areas in many of the drawings reproduced in his book.)