I borrowed it from the library earlier this year or last year when I think it was fairly new. Can't remember the author.
It was about a young man in New York who found out that he was the sole heir to the whole of Manhattan and he and a native Indian woman went on the hunt for some documents to prove it, following clues across NY.
It was a fairly light book and I think it was called something like The Legacy (though not that).
Does it ring any bells with anyone?