Pretty damn good fantasy. The best part: it doesn't read like a modern Tolkein-wanna-be with elves, dwarves and the usual allotment of fantasy creatures as people embark on a quest, and blah-blah-blah. What we have here is a serious attempt to create a world that is full of just enough side-referenced mystery to keep you asking questions, to keep you wanting to know more about the broader world, and anxious for more.
Butcher does a great job developing characters, especially among the Marat people, whose politics and society I found a fascinating blend of Native American and indigenous African cultures. The broader plot line is one of political betrayal and treachery, standard enough, but hidden behind layers of other major events and thematic developments including clashes between cultures of civilization and nature, adolescent growth and development, love, and an interesting kind of class struggle between those who can use furies (or magic) and those who cannot. The whole notion of furycrafting is an intelligent and original take on the use of magic in fantasy stories and making Tavi, the main character, someone who lacked that ability, while surrounding him with very powerful crafters helps the reader sympathize and identify with him.
One other thing that Butcher does amazingly well: suspenseful action. Once you hit the back half of the book the action is non-stop and relentless in a very, very good way. The story was a little predictable, especially with the appearance of a legendary figure in an unassuming one (too much coincidence and melodrama for me), but it was still highly entertaining and fun to read.