That’s interesting to know. I tried the first couple a few years back and decided they really weren’t for me – I found them pretty tedious tbh. I might have another crack at them if the first couple are a bit below par.
I did exactly the same. I read The Colour of Magic and The Light Fantastic, then thought “I don’t understand what the fuss is about” and didn’t go back to them for years. I was persuaded later to go back to them by a mate who had the full collection (at the time) so could lend them to me. Equal Rites is better, and Mort is probably the one where he first looked at the end of his legs.
I think there’s merit in starting at the beginning with the acceptance that they’re weaker titles. If you just want to jump in without committing to anything I’d probably start with Mort.
I’ve never done it but you could always try reading them by theme rather than chronologically, the Witches saga, the Watch/Vimes stories or the Death stories all and up on their own merit if you wanted to dip into it.
You could, and there exists reading orders online like flow charts. But I think you’re better off bouncing between themes for the variety, I think doing it that way might be a bit claustrophobic.
In the earlier books Pterry spends a lot of time explaining the world; as you get later on tails off as it’s assumed you know and retelling the same thing over and over for a quarter of a book would be tedious. Like, just imagine if every Spider-Man reboot started with an origin story, that’d just be, er, oh.
Plus one thing that does progress as you go through the books is time. Certainly in the later books, technology advances.
If you’re going to read the series I’d do it in published order. If you just want one at random then either first-in-a-series or a standalone. Something like Unseen Academicals has little bearing or reliance on anything else, and he even manages to make a book about football interesting.