I'll say Wolf in White Van by John Darnielle. It's a non-linear story about a disfigured suicide attempt survivor undergoing litigation because he created an immersive fantasy game and two kids took it too seriously.
....Wow. Trying to boil it down to one sentence does not do it justice. But fundamentally it's a book about loneliness and how that can affect people in surprising and different ways. The loose, jumping timeline makes it feel like you're watching a car crash video after reading a news story about it: you already know exactly how it's going to end, but watching it happen kicks so viscerally.
And on the topic of John Darnielle, I also love Universal Harvester. It's the least horrific horror novel I've ever read. It's hard to point to anything particularly bad that happens in the story, but the mood is so intense and overbearing that you start to feel trapped, boxed in. There's a trick the author pulls about halfway through that was so subtle but so good: with just one word, the entire story got blown apart in a way that terrified me.