We remember him as a bulldog--squat frame, bulging wide-set eyes, fearsome jowls--but in 1924, when he became director of the FBI, he had been the trim, dazzling wunderkind of the administrative state, buzzing with energy and big ideas for reform. He transformed a failing law-enforcement backwater, riddled with scandal, into a modern machine. He believed in the power of the federal government to do great things for the nation and its citizens. He also believed that certain people--many of them communists or racial minorities or both-- did not deserve to be included in that American project. Hoover rose to power and then stayed there, decade after decade, using the tools of state to create a personal fiefdom unrivaled in U.S. history. Beverly Gage's monumental work explores the full sweep of Hoover's life and career, from his birth in 1895 to a modest Washington of government down to the grassroots, wanted him there and supported what he wasdoing, thus creating the template that the political right has followed to transform its party. G-Man places Hoover back where he once stood in American poli