If it's in a private collection, a scholar who really, really needs to see it might make an arrangement with the owner. For everyone else, though, there are copies at the local bookstore. Bonus, though: if it's in a private collection, there's a chance that it physically is in a library. Some private collections are housed inside public (usually university) library special collections. From the investor's standpoint, it's worth it to have professionals who know preservation keeping the book in climate-controlled, reasonably secure facilities.

It's been a while, but I remember enjoying a lot the very early writings that were collected posthumously in Atop an Underwood, very easy to pick up arbitrarily. Other good ones - Desolation Angels, Dharma Bums, The Town and the City, Subterraneans, Satori in Paris. Those are all formative. There was another posthumous release And the Hippos Were Boiled in Their Tanks which was just a funny and ridiculous retelling of a murder of a friend.

Of course, lots of fun stuff from Bukowski, Gregory Corso, Gary Snyder, Phil Lamantia, John Clellon Holmes, Richard Brautigan, short stories and poems. Neal Cassady Collected Letters, 1944-1967 was probably my single favorite book back then. I'm sure I'm forgetting lots of stuff.

Oh and Dog https://www.youtube.com/watch?v=Hk8cMyCUnoo

It's set in the exact same time and place, and I think parallels the destructive nature of the Road in a more a direct way.

I think the Road is actually best read once as a teenager, once at midlife. The perspective change is enormous.