The Stranger in the Woods of the title is a man, Christopher Knight, who disappeared into the woods in Maine, USA in his 20's and lived in complete solitude for around 20 years. He lived in close proximity to a number of summer cabins, and some all-year-round residents in a small town and survived by breaking into cabins and stealing supplies. Finkel is a journalist intrigued by Knight who corresponded with him and visited him in prison.
It is a fascinating read and Finkel does a good job of telling Knight's story whilst tying it in with historical accounts of hermits and research on isolation. He tries his best not to romanticise Knight and to give the residents who were burgled for years a say, though I'm not entirely sure he's impartial. It makes for uncomfortable reading towards the end of the book, where Knight and his family repeatedly tell Finkel to leave him alone, before he eventually does.
