My Side of the Mountain. Kid gets tired of family problems, runs away to live in the Catskills off the land on an old family farm. Befriends a librarian who lends him books on survival. He makes his own clothes from deer skin, catches his own fish with homemade hooks, lives in a hollowed-out tree, that sort of thing.

I am currently a bushwhacking bookworm. I suspect it was all that book.