When he became director of the FBI in 1924, J. Edgar Hoover was a dazzling wunderkind buzzing with 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 - did not deserve to be included in that American project.

In her nuanced and definitive portrait, Beverly Gage charts Hoover's rise to power, as he used the tools of state to create a personal fiefdom unrivalled in U.S. history. Hoover was not above blackmail and intimidation, and his conservative values ranged from white supremacy to a crusading and politicized interpretation of Christianity. But he was more than a one-dimensional tyrant who strong-armed the country into submission. As FBI director for almost fifty years, he was a confidant, counsellor, and adversary to eight U.S. presidents, four Republicans and four Democrats. His conservative values won him the admiration of millions of Americans. He stayed in office for so long because many people, from the highest reaches of government down to the grassroots, wanted him there. And he has done more to shape the political right today than many presidents.

G-Man places Hoover back where he once stood: at the centre of American political history. In telling his story, Gage shines a light on great social and political changes in 20th century America, from policing and civil rights to political culture and ideology.