Hard to rate, as it's sorta more a utility than a learning text - about as engaging as reading the dictionary, but if you sit down, focus, and parse through the dry language, it's going to tell you exactly the facts. Lot of good here, and would, I think, be a good classroom resource or reference guide.
I did, as a note, read this as an eBook so many of the example images were lost on me - An interesting exercise reading a book about color in black and white, but not one I'd suggest if you can avoid it.