As a "guide for professionals and hobbyists" I think it's probably of more use to professionals. As a hobbyist I did find the history of wargaming interesting, but the sections on designing and developing wargames seemed much more aimed at the professional.

In this sense professional refers to those who play wargames for a living, not those who make them. In other words, military officers and others who use wargames in their profession.

Admittedly, I last read this book around ten years ago. Since then I've read quite a bit more on game design, and a return to this book today might yield more interesting results.