Quite a few of the folks on my blogroll seem to be fond of Terry Pratchett's "Discworld" books. To my everlasting shame, I've never actually gotten around to those.
I'm currently finishing up Stephen King's Dark Tower opus, but will be in need of another multi-volume saga when I'm finished. All you Pratchett fans--why is it imperative that I read those books? Give me your best one-sentence salespitch to reel me in.