House of Echoes by Brendan Duffy
So, I was almost late to work because I had to finish this book! Couldn't put it down! It has an old Mansion in the mountains of New England, a young family from New York who buys the old place to turn into an inn, and they have a curious boy who likes to play in the woods. Oh, yes, there is also a sinister watcher in those woods and the small village has an interest in the family genealogy of this young family. Is that enough of a hook for you? I hope you enjoy it as much as I did.