This is one of the best books on color theory. I own several and would like to own this one, but I believe it is out of print. That's okay, though, because when I want to look through it again, I can just go to the library! :)
She explains how different colors work together more than other books on color theory. She breaks things down and explains things better than any other book I've read on this topic. I would recommend this book for anyone who is into watercolors.