Inside the Cage by Matt Whyman.
I had intended to tell you guys about it earlier, but it slipped my mind.
It raises human rights issues around camps such as Guantanemo Bay. It's very much no holds barred in terms of the violence that is described.
I would recommend it for ages 13+ as long as you're not into censorship. (My 10 yr-old read it and I was fine with that, but some parents wouldn't be.)
ANYWAY it's in the Book People Sale - 3 books for £6, so if there are other books you want it's an absolute bargain.