Been a huge Pratchett fan for years. Read every Discworld novel at least twice, also Good Omens, Nation, the Nome trilogy, and his oddball early work like Carpet People, the Johnny adventures, and assorted sci-fi books. I even have a copy of "Where's My Cow?" that I'll be reading to mini-Jokers someday.

I'd actually say his Dark Side of the Sun is one of the most delightful and unusual sci-fi books I've ever read, while Strata is clearly the precursor to what would eventually become the Discworld.
Favorite Discworld novel would probably have to be Men at Arms - a ripping good yarn, but also a triumphant character tale for Sam Vimes, one of his best protagonists. The other Guards books are also excellent, but only Night Watch comes close to being as good. It's tough to pick a true favorite, though, as they all have something special about them: Small Gods, Monstrous Regiment, Soul Music, The Truth, Moving Pictures and Interesting Times are equally among his most hilarious and insightful.
First Pratchett book I ever picked up was Interesting Times, but I was only 13 or 14 and barely understood anything about his philosophical introduction, so I never got into it at the time. Tried again a year or so later, and it finally clicked - after reading that and Soul Music, I was completely hooked!
I do wish they'd turn the Night Watch series into a "police procedural" like TV series. I think it would be awesome.
I agree, or even one of their great TV-movies like they did for Going Postal et al. The attention to detail was amazing, would love to see the Guards get the same treatment - but only if they can get Eastwood for Vimes.