If you're not aware of it, the Annotated Pratchett File¹ is a joy for the dedicated Pratchett reader. It collates explanations and observations on the many, many well-layered jokes in his works. I read a lot and felt like I was getting some pretty obscure jokes, but the APF opened my eyes to historical and cultural allusions that had whooshed en masse over my head! I'm in awe at Terry's erudition. I wish he was still around writing for us :'(
To truly get every joke you need a very in-depth knowledge of ancient, medieval, and modern history and literature. Even his basic puns often as not pull from famous European poetry or art.
The obvious send-ups are east to identify but reading through APF gives you the full depth, and it’s pretty incredible.
¹https://www.lspace.org/books/apf/