The Edge of Being — James Brandon

A tender and heartfelt queer YA novel about the multiplicities of grief, deeply held family secrets, and finding new love.

Isaac Griffin has always felt something was missing from his life. And for good reason: he's never met his dad. He'd started to believe he'd never belong in this world, that the scattered missing pieces of his life would never come together, when he discovers a box hidden deep in the attic with his father's name on it.

When the first clue points him to San Francisco, he sets off with his boyfriend to find the answers, and the person he's been waiting his whole life for. But when his vintage station wagon breaks down (and possibly his relationship too) they are forced to rely on an unusual girl who goes by Max -- and has her own familial pain -- to take them the rest of the way.
 
As his family history is revealed, Isaac finds himself drawing closer to Max. Using notes his dad had written decades ago, the two of them retrace his father's steps during the weeks leading up to the Compton's Cafeteria Riot in San Francisco, a precursor to the Stonewall Riots a few years later. Only to discover, as he learns about the past that perhaps the missing pieces of his life weren't ever missing at all.