Suggest me a book about regret, or where regret is a main theme, or where regret is a primary component of the plot

My reading tastes are pretty broad and so I’m open to most genres except:
– Not romance (although I wouldn’t necessarily be opposed to a book where the regret is one related to a relationship)
– Not YA

Bonus points if the book features genuinely good writing / a more literary style (i.e., it is more than the plot/story/premise that makes it good). I’m open to contemporary works or classics! When I began writing this I had fiction in mind but I suppose a good non-fiction work would also be okay.

Thank you for any thoughts 🙂

by FancyDonut