The book is well worth buying just for the brilliant chapters on making the rig work. The explanations and guidelines are the best we've come across anywhere. The information content is higher in the Gaff Rig Handbook . The text uses clear, plain English, with a lot to ponder on each page. It's loaded with with extensive and detailed line drawings showing rigging details, approaches to gaff sail making, and varieties of sail layouts and hull profiles.
Photographs are frequent, large, clear and carefully chosen to illustrate points made in the text.
Really, you need this book for the technical side and Hand Reef and Steer for the sailing.