Hogfather

It's that time of year again. Hogswatchnight. 'Tis the season to be jolly, to hang mistletoe and holly, and other stuff ending in olly.
'Tis the season when the Hogfather himself dons his red suit and climbs in his sleigh pulled by - of course! - eight hogs and brings gifts to all the boys and girls of Discworld.
But this year, there's a problem. A stranger has taken the place of the Hogfather. Well, not exactly a stranger. He's actually pretty well known. He carries a scythe along with his bag of toys, and he's going to SLEIGH everyone he sees tonight.
The switch has been arranged by the Auditors, mysterious superbeings who want our universe to be a collection of rocks swinging in curves through space. Life is messy. Why not get rid of it? And who better than - you know who?
Somebody has to rescue the real Hogfather before this morbid impostor tracks soot on the world's carpets. It's up to Ankh-Morpork's intellectual elite, the assembled wizards of Unseen University - with the help of a monster-bashing nanny, the world's worst inventor, plus a bona-fide, honest-to-god god (the oh god of hangovers, to be precise) - to come up with a plan to save the universe.