Under Heaven by Guy Gavriel Kay.
Absolutely stellar book. It's absolutely no surprise that it's been named by at least 5 publications as "best fiction of 2010." It's about an alternate 8th century China, where a young man can suddenly influence the future of an empire. The story is riveting and doesn't let you go. The characters are ALL developed incredibly well. Main characters and minor characters all are fleshed out. An amazing book, I highly recommend it to anyone who enjoys historical fiction..
as an aside, I didn't know until I looked him up that Guy Gavriel Kay was the guy who edited Tolkien's stuff after he died. no wonder he's so amazing. I'm definitely going to pick up some of his other books now, when I get the time.