I read several of his very early Discworld books when I was still in high school, probably around 1988. The fact that I read *several* is more an indication of how much I read than how much I liked them, but I actually stopped reading them before I ran out of them to read, which *was* an indication of my dislike. It wasn't Pratchett in particular; I eventually realised I didn't care for most satire in prose form.
In 1996 I was flying all around the country meeting Internet friends, and somewhere around the DC airport I ran out of books. In desperation, I bought SMALL GODS, not because I thought I would like it, but because I figured I knew what I was getting, which is worth a certain something when you're stuck on an airplane for several hours.
To my complete surprise, I loved it. LOVED. IT. It was--it was written by the same person, clearly, but it was on a whole different level from the early books I'd read. It was funny. It was poignant. It was clever. It was intelligent. It had a turtle, and I love turtles. In fact, possibly I love turtles so much because of SMALL GODS. I bought a turtle necklace that weekend because I loved the book so much. I still have that necklace.
I read about six more Pratchett books that week, and thought they were all good. It's not that I started to like prose satire, because I still mostly don't; it's that Pratchett got better. A lot better. Which should, I think, be a heartening thing for any writer to encounter: another, wildly popular, writer who visibly improved in his craftsmanship as his career progressed.
I've read him on and off since then, not with anything even vaguely resembling consistency, which means there's still a lot of Pratchett for me to read. Airport books: I'll read them when I need to know what I'm getting, and I'll know it's going to be something good.
I am so, so heartbroken for all my friends who were friends of his, and for the innumerable people whose lives he touched more profoundly than mine. I would have liked to have met him; in the end, I'm a fan after all.