A fun read. No messy chapters to interrupt the flow or suggest that maybe you should stop now and go to bed. Just the occasional footnote that makes you stop everything and focus on it.
So the Auditors - that mystical group of beings that have an aversion to life, belief, or well, anything that isn't a rock, have decided that Hogfather must die. And of course, mayhem ensues.
I've seen the movie, and it does follow pretty close.