Count Karlstein, or the Ride of the Demon Huntsman - Philip Pullman
Anyone who hasn't been living under a rock for the past few years will know Pullman's name, as he's written the phenomenally successful Northern Lights trilogy, the first of which has been made into a movie, and other equally successful YA books.

This was his first novel, republished, and unfortunately it shows a little. Count Karlstein isn't a bad book, it's just a bit predictable from quite early on - the moment the missing heir is mentioned, for example, it doesn't take a rocket scientist to figure out just which of the other characters he really is. There's also a few too many coincidences for my liking, though it was a pleasant enough read.