Who would've thought, after reading the first few books of Terry Pratchett that this writer would one day produce a book with such depth as this one? Okay, as always it's all wrapped up in a high speed, intricate story with several sub-plots, but that makes the ultimate message Pratchett delivers only more convincing.
So, what's the story all about? As always, the Discworld is in perilous danger, or at least civilization on it is. The "Auditors" (of reality, not money) want to eliminate mankind. Since these beings like everything to be orderly, precise and regular, it's not hard to imagine mankind is a thorn in the eye to them. The way they plan to wipe mankind of the disc is by murdering the Hogfather (Discworlds equivalent of Santaclaus), a job assigned to the less than sane assassin Teatime. DEATH, the only one who understands the danger mankind is in, can't help himself and interferes by impersonating the Hogfather. Meanwhile his granddaughter Susan sets out to stop Teatime (with a little dubious help from the Oh-God of Hangovers). Of course, in the end all's well, but not before Pratchett makes a very keen observation of what defines humanity. Believing in certain 'lies' (like the existence of a Hogfather) is, according to Death (the only truly impartial observer) what makes us human.
I've read the book three times now and I'm still surprised how well Pratchett builds his story and every time I marvel at the insights he shows in what humans are like. It's a very special book, with something for everybody and I really recommend it not only to Pratchett fans.