For books of this type, go for Never Let Me Go, it's much better. I can see how this might have been longlisted for the Booker prize, but I'm not sure it will make it through to the shortlist. For me, it offered a lot in the way of the idea, and how it might unfold, but actually didn't progress very far. It seemed quite linear, and the protagonist didn't seem to be challenged very much, there didn't seem to be much progression. Also, the hints at the start of the book imply she is going to do a 'big thing', and the final act doesn't quite seem as powerful as the promise.