The description of the book, when I saw it in this post, intrigued me, so I downloaded it and have just completed it. It's fantastic. I urge others, young adult or not, to do the same. It succeeds fantastically as a coming-of-age novel, and a time travel story, and it probes issues of slavery, ancestry and racial identity with a deft touch.
In short: loved it, loved it, loved it. I'm adding it to my daughters' dad-says-you-have-to-read-this lists.