Perhaps the most valuable aspect of this work is "The Grammar of Heraldry." It comprises descriptions and sketches of the elements of heraldic art suitable for the development of one's own coat of arms. From the information included herein, one can not only pick the appropriate elements, and blazon them properly, but also defend one's choices from the stand point of an acknowledged master in the field. This edition was "revised and enlarged" by the OTHER master of heraldry, A. C. Fox-Davies, making it as definitive a work as can be found today.
The fifth star was withheld on the grounds of its readability for a twenty-first century reader. It is a revision of a work written in the late nineteenth century, so the style clearly demonstrates the era's slower approach to life. However, if you "play" with heraldry (SCA, Rennies: Listen Up!) you should have the book on your shelf.