What's the darkest book/story you've ever read?

@GlassDog "The Trial" is on an entirely different level, compared to most books recommended in this thread (such as splatterpunk).
I don't know "The Wasp Factory".

@helenS I feel a bit hesitant to recommend it because it left me in a slough of despond for months after reading it. I haven't read The Castle, but I'm intrigued by the idea, even if it might be bad for me.

I'm not sure I'd recommend The Wasp Factory to you. Its aim is to shock.

@GlassDog I've read both, the Castle and the Trial, and The Castle is much more radical, in my opinion. I would say it's his masterpiece.

@helenS A colleague feels the same, although I'd take your opinion above his because you've read both.