Stephen Maing and Brett Story’s documentary Union is one of the best American films about the labor movement since 1940’s The Grapes of Wrath. Using cinéma vérité “you-are-there” film techniques, Union chronicles the fight to organize the JFK8 Amazon fulfillment center in Staten Island, New York. Union, a Sundance Film Festival Special Jury Award winner, focuses on fired Amazon worker Chris Smalls…