I've actually been wondering about the value of fictional evidence. Particularly reading a pile of Hitchens book reviews, wherein he strongly advocates good fiction for its power to explore and teach you how humans work. Off the top of my head I can think of more accurate methods, but stories are natural to humans so may well be a much more powerful vector than popularisations of psychological research. I'm not entirely convinced by the Hitchens line but was surprised to see him pushing it so vehemently.

Edit: Wei Dai addressed this point a couple of years ago, with Fictional Evidence vs Fictional Insight.