I just picked up a used copy of Impromptu Man. It is good to get Moreno's history and theory straight from his son. If you haven't read any Moreno yet, I would encourage you to do so. He is the father of psychodrama and many of his ideas were adopted by other counseling theorists.
Fun Fact: Moreno hung out with Adler and other "intellectuals" in Vienna at Cafe Central and referred their patients to each other. They attempted to replicate these gatherings in NYC with each other and other "intellectuals."