One of the best SciFi writers ever. Also, the mind behind one of the best StarTrekOriginalSeries episodes, "City On The Edge Of Forever", and Conceptual Consultant for BabylonFive.
Famous for his irascibility.
See also http://www.islets.net/islets.html
I haven't read much of his stuff, but i don't think he's very good - certainly not "One of the best SciFi writers ever". Maybe he's just not to my taste. -- TomAnderson