Books with themes of existential longing? Books that express the inexpressible?

Sorry if that's a bit too vague. Some of my favorite books are I'm Thinking of Ending Things, Foe, Catcher in the Rye, Franny and Zooey, The Bell Jar, My Year of Rest and Relaxation, The Brothers Karamazov, Earthlings… Few books have impressed me like some of these. There's just something about them. I'm looking [...]