The Unnamable (1953)
by Samuel Beckett
The Unnamable is the final novel in his so-called trilogy, which also includes Malone and Molloy Dies. The Unnamable is the most abstract of the bunch which seems to be "simply" a stream of consciousness narration from an immobile character who, I thought, was burning in some kind of eternal hell fire. I can't find any support for my theory that the narrator of The Unnamable is literally trapped in hell, but I suppose you could explain the hell references as exaggeration for narrative effect.
The saving grace of The Unnamable is that it is only about 130 pages long, otherwise you'd be looking at something as difficult to get through as Finnegan's Wake. No plot, no characters, no location, no time, just the stream of consciousness narration.