I have a friend who rereads Doomsday Book every Christmas (except the past two years, for obvious reasons). I'm not that dedicated, but it's one of my most reread books.

To Say Nothing of the Dog is one of my comfort reads.

Last of the Winnebagos was the first thing I read by her, and it's probably the best story I'll never read again.

I like a lot of her other stuff, but those are my top three.