Adult protagonist in their 30s

It’s been a while since I’ve lost myself in a book. I’ve been feeling melancholy as of late. I fear I may be a bit depressed. I’m looking for a book that is thoughtful, whatever that means to you. I’m not looking for anything particularly funny or lighthearted, neither am I interested in romance. I’m not trying to shake the sadness. Maybe just something to keep it company.

My only other condition is that the protagonist be at least in their 30s or older. Thank you in advance.