Probably The Third Policeman. I had totally forgotten why it was on my to-read list, so I thought it was just a generic mystery novel coming in... it wasn't that. It actually did start out like a crime novel with some slightly weird undertones, but then it just took a sharp left turn and went totally off the rails. Completely wild book—it's complete nonsense that makes sense in a dream-logic sort of way. I've read a lot of books that try to read like dreams, but they're always either too internally consistent or fall apart completely; The Third Policeman is a rare book that actually pulls it off.
What really pulls it together is the language. The language is the internal logic that keeps the book flowing: nothing in the book makes sense if you think about it conceptually, but it's kept together through what I can best describe as a sort of language association game. At one, point, for example, the main character has forgotten his name, so he makes up with a list of names he might have had:
Hugh Murray. Constantin Petrie. Signor Beniamino Bari. The Honourable Alex O'Brannigan, Bart. Kurt Freund. Mr John P. deSalis, M.A. Dr Solway Garr. Bonaparte Gosworth. Legs O'Hagan.
Then his conscience—named Joe—goes off on a tangent about the just-made-up Signor Beniamino Bari:
Signor Beniamino Bari, Joe said, the eminent tenor. Three baton-charges outside La Scala at great tenor's preimere. Extraordinary scenes were witnessed outside La Scala Opera House when a crowd of some ten thousand devotees, incensed by the management's statement that no more standing-room was available, attempted to rush the barriers. Thousands were injured...
This random story about a totally made-up name goes on for a couple more paragraphs. Then there's another one about Dr Solway Garr, until the main character—still nameless—has had enough:
I think that is quite enough, I said.
...and then none of the names or stories ever come up again. Almost everything in the book is like that: here for a moment, gradually transforms into something totally different and then never comes back. It's something between watching improv and dreaming.
And sometimes the language is just hilarious on its own. Random phrases just totally got me on occasion:
It is nearly an insoluble pancake, a conundrum of inscrutable potentialities, a snorter.
Not a bad descrption for the whole book, really!