A documentary directed by Alex Gibney (who just won an Oscar for Taxi to the Dark Side), dutifully covers the swath of the mad doctor’s writing, but it is chiefly interested in Hunter S. Thompson the political animal—the man who dogged Nixon through New Hampshire and found his own reflection. It was part of the American genius for polarization that Thompson saw Nixon as his doppelgänger, his mirror. Nixon was his dark shadow. Or maybe it was the other way around. So it makes perfect sense that when Gonzo recounts Thompson’s last serious journalistic assignment—sent to cover the 1974 Ali-Frazier “Rumble in the Jungle” fight, he swallowed a cabinet of pills and wandered off to float in the hotel pool—Gibney re-creates the scene with washed-out footage of azure water and a man in a Nixon mask. The image is inspired on a number of levels, since this was the moment when a genuinely gifted writer decisively sacrificed his talent on the altar of indulgence, and when he slipped on a mask of celebrity that he would never remove. The rest of the movie, while amusing and honest, doesn’t often approach that level of perception. There are plenty of guest appearances by old cronies, few of whom can stir themselves enough to say an unkind word about the man who squandered his last two decades shooting rifles on his ranch until he finally turned a .45 on himself in 2005. R. AARON MESH