No question this is a beautiful book, and I often have my own copy open to enjoy the excellent reproductions of drawings by masters past and present. The text, especially the chapter on composition, is very thorough and persuasive.
The crux of my growing discontent with the book is the demonstration on how to copy an old master drawing, a drawing by Raphael. It's an impressive performance, accomplished, like most of the projects demonstrated in the book, using the straight line block-in method, and the final result is a near-exact duplicate of the original drawing. The problem is: Raphael didn't draw this way. Neither did Michelangelo, Pontormo, Rubens, Van Dyck, Rembrandt, Prud'hon or Ingres.
There is much which is of value in this book, but in order to understand drawing in a wider context, I would recommend, in addition, anything by Robert Beverly Hale, Burne Hogarth, George Bridgeman, John H. Vanderpoel, or Harold Speed. Also, I highly recommend "The Language of Drawing" by Sherrie McGraw, which is a pointed and subtle rebuttal to what some might see as the over-emphasis on accuracy in the methods taught in this book.
Drawing is a big subject, and no one book covers it all.