It depends a little on how advanced the 16 year old is. "How the Mind Works" by Steve Pinker is an excellent introduction to both computation theories of mind and evolutionary theories of mind. The sort of book that brings up lots of issues that get discussed here: what is free will?; how do culture and psychology interact?; what exactly is a computational theory of mind? etc etc.
If you want to go for SF I would highly recommend any of Greg Egan's books. These cover the gamut of Extropian topics (e.g. uploading, nanotechnology, alternate universes, bio-high-tech etc.). Sometimes the characterizations are a little weak, but this is more than made for by the brilliant ideas.
Patrick Wilken http://www.csse.monash.edu.au/~patrickw/ Editor: PSYCHE: An International Journal of Research on Consciousness Secretary: The Association for the Scientific Study of Consciousness http://psyche.cs.monash.edu.au/ http://www.phil.vt.edu/ASSC/