In high school, it was When the Legends Die by Hal Borland. I started reading it on a Saturday morning and didn’t put it down again until late Sunday night.
When I was at Fort Snelling in the '80s, it was Going after Cacciato by Tim O’Brien. Anyone who’s ever served in the military would understand why.
And in the '90s, it was Gone South by Robert R McCammon. I once bought a copy for one of my Russian girlfriends. When I saw her a week or so later, she was horrified. She asked “Why did you give me a book like that? It’s full of freaks and drug dealers and people shooting each other!” All I could say in reply was “Read it all the way through, right to the very last page, and you’ll understand why I bought it for you.”
All three books spoke to me on a very personal level. At the age of 17, I identified with Legends more than any other book I’d ever read.