I'd find a Pratchett Discworld book that didn't have TOO adult a theme. I guess it depends upon the kid's maturity, but when I was 11 I was reading adult fiction already. The Tiffany Aching books are good, but you kind of have to know the world to really get them.
Honestly, Harry Potter is good stuff for kids that age, I think. Or... just give the kid something YOU like that doesn't have too many themes/scenes that worry you. Let the kid read up to the material.
When you have to use a public toilet (this includes the ones at your workplace), do you prefer the seat to be warm or cold?