Book about male mid-life crisis (but not parent-focused)

Maybe a bit niche, but as the title says I'm after a book featuring some aspect of the male mid-life crisis. However, the handful I've encountered focus heavily on kids having left home (what's the point of me now they've flown the nests etc) and I'm looking for something that might be relevant to someone who's had no kids. I doesn't have to exclude kids, just not have that be a heavy focus of it.

Fiction or non fiction is fine, set or written in any year or era. Just not the Hitchhiker's Guide to the Galaxy, please.

Thanks for any suggestions.