I've been meaning to read this book for forever; I've loved everything else I've read by GGK and this is one of those series that everyone has kept telling me to read.
And it's worth it. GGK is JRRT in the best way--he has a sympathy to the complexity of the world and characters in a way that echoes JRRT.
He also...trips over some of the same things that JRRT does, but he's still miles ahead--especially in terms of female characterization--even than many contemporary authors.
If you've ever wondered what the mythologies of The Dark is Rising Sequence written for adults would be like, it's this.