My DD13 has similar requirements/tastes in reading, it sounds like.
John Grisham? Dan Brown?
Do be aware that far more Fantasy literature has "adult" content than might be desirable.
Piers Anthony's novels are not fine literature, but they are 13yo-friendly and amusing-- and there are a LOT of them. (Bonus!)
I strongly recommend The Hitchhiker's Guide. My DD's favorite book ever, I think.
If he enjoys humor, he might like the Patrick McManus books.
In nonfiction--
The Search for Schrodinger's Cat
All the President's Men
The Making of the Atomic Bomb
