Don't Let Go — Elisabeth Staab

Evergreen Grove, Book 6

Left behind by everyone he's ever loved, Alonzo Grover lives as if there's no future. The discovery of a letter from his deceased boyfriend breaks him out of his rut and spurs him to right an old wrong, but the local stick-in-the-mud sheriff's lieutenant seems determined to ruin all his plans.

Lieutenant Sebastian Haas despises tangling with his small town's most promiscuous party kid. Alonzo's youth and recklessness drive him crazy in more ways than one… As does the uncomfortable secret they share. But when Haas's estranged family arrives in town to throw a wedding he wants no part of, he ends up jumping into Alonzo's car to avoid everyone.
Together, they wind up on an unexpected road trip. When they hit one setback after another, it looks like they might kill each other before they make it back home. Unless they find something better to do than fight.