The authors cracked the secret filing system of J. Edgar Hoover, head of the FBI until he died in 1972. This is his definitive biography with unprecedented accuracy and comprehensive primary evidence. Draws on previously unknown and extremely sensitive FBI files as well as interviews with Hoover family members, agents, politicians, and "targets" of FBI investigations to reveal the man, the administrator, and the power-monger who manipulated American politics for half a century. Investigates the extent to which "Hoover made a mockery of the American Constitution and its system of checks and balances" by immunizing the FBI from critical scrutiny.