The Knife of Never Letting Go by Patrick Ness
There is a reason why this has won lots of prizes - it's incredibly good. Try as I might to limit the amount of teen fiction I read, I am very grateful for having discovered this remarkable writer. It would not be an exageration to put this in a list alongside Holes, How I Live Now and A Gathering Light, it's up there with my all time favourite teen modern classics.
You will read this at speed and reflect on it at leisure (that is until you manage to get your hands on the sequel, Ask and the Answer when you will simply start reading it immediately at the expense of whatever it was you were meant to be doing). Patrick Ness raises big issues of morality and sexual politics while sticking to the maxim, 'show, don't tell'. I cannot recommend this highly enough.