I thought the humor in the Scanner Darkly movie was there in the book already. Any examples of what you're thinking he added?
I've read Ubik. That might have been my favorite. There's a podcast called The Philip K. Dickhead's podcast that covers all of his novels. I haven't listened to that much of it, and only for some things that I have read recently or some of the books they covered from other authors, so I haven't listened to the Ubik epsiode because I read that years ago, but at some point I remember one of them saying that they thought Ubik was similar to and not quite as good as his earlier book Eye in the Sky. Have you read that one? I haven't but I own it, and plan to read it and reread Ubik in the near future.
FWIW, J-Ro said that he liked Eye in the Sky more than most of the books in the Library America sets.
The cover of my copy
is shit compared to the original
Linklater wanted to do Ubik, in fact I think he wanted to do it before A Scanner Darkly. I don't know if that's still in the cards.
I never watched the Man in the High Castle series. I heard that the first few episodes were like the book, but after that it goes in a totally different direction.
The next Dick novel I read is probably going to be Deus Irae, his collaboration with Roger Zelazny. I think it has an iffy reputation, but I'm curious.