by Jean Craighead George
The book follows Sam Gribley, a 13 year old boy from New York City, who chooses to reject urban life, and runs away to his great grandfather's old abandoned farmland in the Catskill mountains to live off the wilderness. He brings with him a penknife, a ball of cord, some flint and steel, 40 dollars he earned from selling newspapers in the busy streets of New York, and the knowledge he gathered reading books about survival.
When he finally gets to the Catskill Mountains, he slowly begins learning the practical aspects of wilderness life, applying the things he read while preparing. He perfects the best ways to fish, starts to orient himself, and learns to forage. He burns and chops out a hollow in a huge hemlock tree to serve as a shelter. He hunts, lays traps, and manages to capture and tame a baby peregrine falcon who he names Frightful, who helps him catch small animals.
As summer passes, gets used to living off the land. He makes new clothing out of hide, builds a bed, and prepares for winter by laying in preserved food, firewood, and building himself a clay stove to keep warm. He becomes accustomed to the wilderness and befriends several of it's animals, including a weasel which he names The Baron, and a raccoon he calls Jessie Coon James. He sometimes walks to the nearby town to do research at the library.
Time passes and people start to notice the living presence in the forest. Sam has a series of visitors, including Bando, a professor who got lost while hiking in the forest. Bando and Sam become fast friends, and teach each other things about the forest and about life. After Bando leaves to go back to his university for the fall, Sam encounters a young reporter who wants to find out about the rumors of a mysterious wild boy living in the forest. When Sam lies and pretends to be someone else, the reporter quickly figures out that Sam, clothed all in hand-stitched deerskin, is the "wild boy." Sam agrees to let the reporter come back the following spring and learn from him in exchange for not telling the world about where Sam is.
At the end of the book, Sam's family comes to find him, having been worried since he left. His father has decided that since he can't stop Sam from running away to the woods, the entire family will move there, build a house, and try to farm the land. Sam is disappointed at the idea of giving up his tree-home and living a more normal life, but his parents tell him that that's the way it has to be until he's 18.
(summary from wiki)