As for the book, it was one of the first I read. I always thought it made so much sense for Death to be the Hogfather, since so much of the tradition was tied to death. Hogswatch (and every winter solstice holiday) was always about the fear of death, and ensuring life for another year. I think it actually ties in well to Pyramids, where the belief that the pharoah makes the sun rise doesn't ensure that a ball of fire keeps going around the disc, but it does make sure that the "sun rises".
I've always found Pratchett's explorations of how belief influences us and the world around us, and how we use belief to shape the outside world, to be one of his greatest strengths as a writer, and one of the best things about the Disc.
I especially like the tie between the old and new traditions and how easy it is for us to forget or ignore the past. We never really understand how important these traditions were for our ancestors and how they shaped the way we currently see the world. It made me appreciate how nice it is to live in a world where we don't worry that the sun will never rise again. But perhaps we've lost something by distancing ourselves so much for those roots.

