Beacon by Claire Kent

It might have taken ten years for Mack to fall apart, but now he has disappeared.

He’s been the heart of our community since Impact, keeping all of us alive in a hostile, unstable world. Now he’s been hurt after fighting one too many battles. He’s retreated into a massive, dangerous forest to live on his own, and he won’t come out.
Mack and I had an on-and-off relationship for years, but it’s always been no strings attached. After a toxic marriage, I can’t commit to another man until I’m confident I can stand on my own. But some things are more important than the emotional baggage I’ve always carried. Mack is more important.
And it’s time to bring him home.

Beacon is a post-apocalyptic romance set in the near future after a global catastrophe, and it includes violence and (secondary) character death. It’s the eighth and final book in the Kindled series.