Yes - he's popular for a reason, not pop, but that he deserves popularity. I wonder about being highbrow... in that yes you're right, that's how he's viewed, and he's well-known and it's fantasy and it's comedic and therefore cannot be highbrow (awful how we judge these things) but he has some very insightful ideas or ethics he wants to communicate. If, to me, lowbrow vs highbrow is about depth or insight, or long-lasting value in literature (will he be read in a hundred years? Yes), he is high, even if 'easy'. You're absolutely right, 'masterful' in style.
He writes sentences around how they're, eh, delivered? Can't think of a better word. Lots of footnotes and clauses and parentheticals. And the timing of his words make the jokes.
Well, I think the wisdom is too neatly packaged (basically: Vetinari speaks, so listen you pillock) and his simplistic views often hamfisted by shaping the world to make them sound Right^tm to be "highbrow" per se, but still, it's not for the idiot either.
> He writes sentences around how they're, eh, delivered? Can't think of a better word. And the timing of his words make the jokes.
You put the words in my mouth, very accurate way of describing his style!
His stories are beautiful. The language is very ordinary. (Not a criticism.)
I would absolutely call him a landmark writer, but I wouldn't call him lit fic in the publishing sense.