Since there’s been a bunch of Vonnegut talk lately, I’ll add a couple recommendations from authors I think you’ll enjoy if you already like Vonnegut.
Kafka On the Shore by Haruki Murakami
This will take a bit of adjustment. It reads like a fever dream compared to Vonnegut, but philosophically has similar themes.
Anxious People by Fredrik Backman
Backman has a very similar voice in his writing style. There’s no fluff in his sentence structure, it’s very brief and direct, like Vonnegut, he says what he means to say; however, that does not take away from the emotion and impact of the book.
Not trying to turn this into a reddit-level trigger-warning, but since it’s such a impactful topic you should know that both of these books deal with the subject of suicide.