This is undoubtedly the master work on this glorious artform of the celts, picts, norse & la tene cultures.
George Bain's book is profusely illustrated with pages and pages of his technical and artistic work, as he tried to derive the rules of construction from the standing stones and ancient books. And what a great job he did.
This is undoubtedly one of the finest books I have ever seen period, and is a treasured part of my personal library. If in doubt, buy it.
On a general note, if you are a beginner this may be somewhat overwhelming in detail, and it may be best to buy this along with one of the more step-by-step beginners guides.