I don't know - there are some novels that I really don't want to see a film version of - and you have managed to pick three of them. I don't think Camus, Sartre or Kafka work in a film medium. I saw someone try a comic book version of Metamorphosis once - and just no. That works because you are inside the character's head, so it becomes less about gross-out and more about the horror of losing control over one's body. The problem with a lot of Croenberg's films is I can't watch them. The Fly is unwatchable for me - so I lose all of the great metaphors. I'm too caught up in being grossed out.
That's not brilliant film-making - so much as just shock for shock's sake?

My niece wisely stated at the age of 9 that certain things work better in books, because you are engaged with the ideas not the shocking and painful visuals.

I know Jorges Borges, and the writer of the Unbearable Lightness of Being, often went out of their way to write unfilmable books. They wanted to remain forever in the theater of the mind, not the senses?