From his rapid-fire stand-up comedy riffs to his breakout role in “Mork & Mindy” and his Academy Award-winning performance in Good Will Hunting, Robin Williams was a singularly innovative and beloved entertainer. He often came across as a man possessed, holding forth on culture and politics while mixing in personal revelations --- all with mercurial, tongue-twisting intensity as he inhabited and shed one character after another with lightning speed. But as Dave Itzkoff shows in this revelatory biography, Williams’ comic brilliance masked a deep well of conflicting emotions and self-doubt.