Hogfather by Terry Pratchett
It's the night before hogswatch. And it's too quiet. Where is the big jolly fat man? Why is Death creeping down chimneys and trying to say Ho Ho Ho? The darkest night of the year is getting a lot darker...Susan the gothic governess has got to sort it out by morning, otherwise there won't be a morning. Ever again...The 20th "Discworld" novel is a festive feast of darkness and Death (but with jolly robins and tinsel too). As they say: 'You'd better watch out...'