I bought the book and found it very helpful, it has so many techniques that would normally take a while of trawling through the internet to find, and the projects in the back are lovely. There's a lot of advice which is very encouraging to new dyers and the steps make dyeing look easier than most other resources.
If you are interested in dyeing plant fibres, then you'll want to look elsewhere as this book focuses on wool and animal hairs and has almost no information about using procion mx dyes for those interested in dyeing cotton or linen etc.
My only other criticism is the spiral binding, lots of people on the American site are saying that it's great as it lets the book lie flat, but when I was reading the book, I found that many of the inside edges of the pages were stuck together around the binding wire which resulted in a few nearly and lightly torn pages