Thompson's The New Policeman, a finalist for the Children's Award in Mythopoeic Literature this past year. I don't vote on those, but my first choice would have been Nancy Springer's Dussie. After that, it gets tricky, as there's Holly Black's Trilogy and Derek Landry's Skullduggery Pleasant and The New Policeman. Oh, and the thing that actually won -- The Harry Potter Series.
As far as I can tell, while the committee was mixed about the quality of the HP series and mixed to negative on the last book in particular, the feeling was that the series was simply too important in its effect on the field not to win, which is legitimate, if regrettable.
The New Policeman was lighter than I had expected it to be. It was a fun read, and a quick one, and the central conceit is very good, but I kept expecting there to be more.
There sort of is more, but not as accessibly as there might be. After each chapter, there's a few lines of sheet music from an Irish tune. I think a CD with the music might have helped. Even the few tunes I listened to helped enhance the reading experience. They're all so bouncy and lively.