Simonton is one of the world authorities on this subject. I have read several of his journal articles, and have perused a couple of his earlier books. I heard him speak at the 2007 National Association for Gifted Children conference, and it is clear that he knows his research base on the issues he writes about. His new book
http://www.amazon.com/Genius-Psych-Dean-Keith-Simonton/dp/08...
should be a good read.