I bought this book quite a while back, when I was just starting to learn how to draw celtic knots. I'd heard it was good and it had been reffered to in a couple of other books I'd read.
The method Andy Sloss has invented is simple and logical. He created it to enable knotwork to be constructed on a computer, and I suppose in this it works well, but for my money, it lacks soul. The knots constructed appear mechanical and rigid, which defeats the point for me since even in the most tightly structured manuscript pages of Kells or the Lindisfarne gospels, there is room for the design to 'breathe'. I much prefer Aidan Meehan's longer winded, but more beautiful dot-grid method.
It's obviously a popular choice and if you like the art you pruduce using it, then more power to your elbow, but I'll leave my copy on the bookshelf.
Or you can buy it, cheap.
In fact, pop around, I'll give it to you.