My 10-year-old reads the Pratchett "kid's" novels on his own (as do I - The Amazing Maurice was brilliant), but the older ones he gets read to him at night, with appropriate commentary interspersed. Although Pratchett isn't all that bad when it comes to things a 10-year-old needs explanations for.
Now, Piers Anthony... shudder. Those didn't last long as bedtime stories. I had read them far too long ago to recall with any detail what a gratuitously dirty old man he is... :-P