Sounds like your kiddo might enjoy 1,2,3...Infinity by George Gamow. Maybe now, maybe when he's a bit older. It depends on what his reading level is. I think I read it when I was around seven or so. It covers a lot of fascinating math topics, and was my first introduction to topology. There is a section where it talks about the fact that, from a topological point of view, you can look at the human body either as a tube that is completely surrounded by everything else in the universe, or as a universe of its own that surrounds everything else.

Edited by aculady (04/07/11 09:45 AM)
Edit Reason: added link