Heinlein wrote some great kids' stuff -- but MONITOR which books your kid reads! His "grownup" fiction is really just adolescent sex fantasy. (I say this from the position of disillusioned fan. hadn't read him since I was 15, reread him, and he wasn't what I remembered.)
His JV books, however, still rule. Asimov's another great one, and IIRC you don't need to censor him.
Chum to Hub, Mum to Cub