Otter: I have a 12yo bookworm DS.
Around 13 I expect to turn him loose on The Star Wars Novels, also The Dragon Riders of Pern series. He still dives happily into Artemis Fowl, Wimpy Kid books, Asterix and Anthony Horowitz anything.
The school have sent him home recently with books by John Grisham, Robert Muchamore (thrillers, but ok I think) and the Mark Haddon hit: The Curious Incident of the Dog in the Night-time... last one I read 6 months ago & thought too mature for him, but cat out of the bag, and all that. I'm sure he's not mature enough to really get the most out of it. He's also enjoying Diana Wynne Jones & probably read for lots more sci-fi (Douglas Adams, Asimov, Ursula LeGuin).
You lad is also old enough, I would have thought, for The Book Thief.
I actually have a HUGE long list of ideas of things he could read (for example: Robert Westall, Warrior Cats, James Herriott (DS loves, lots of rude words!!), Sherlock Holmes), but prefer to let him find his own, mostly.