An alarming and sobering book, comparable to the same author's study on the CIA.
From the 1920s to 1972, the FBI was little more than the personal satrap of J. Edgar Hoover. From the First Red Scare, John Reed and Emma Goldman all the way up to the Vietnam War and the Civil Rights movement - he had almost total control over domestic intelligence. However, the FBI also acted as a foreign analysis and counterintelligence bureau, counteracting or competing with the CIA on multiple occasions.
Their record was mixed, at best. Some of their best successes were in World War II - completely destroying the German espionage network in the US for example, but they completely missed Pearl Harbor, despite having broken the Japanese code.
Eisenhower was a cooperative ally, trying to get intelligence on the Soviet Union (which was a success). Under the LBJ administration, Hoover was determined to smear Martin Luther King, whereas LBJ wanted to smash the Klan (which they did!) They did, in fact, keep tabs on the sexual liaisons of senior government officials, and Hoover did threaten Kennedy at least once with this information. Nixon was too paranoid even by their standards, demanding information on connections which did not exist. When even they balked at breaking into the Dem's headquarters, he organized the Plumbers and did it himself.
Like the CIA, the FBI had its own foreign interventions. In one instance, an FBI informant took power in the Dominican Republic.
After Hoover's decline and fall, Nixon's administration fell shortly after, and the organization had nearly destroyed itself before it could be rebuilt again. Some directors were weak, and others were openly disastrous - Louis Freeh, instead of investigating the budding Middle East terror networks like the CIA, refused to speak to Clinton at all and made the now-baffling decision of allying with the Gingrich congress and prosecuting Clinton for perjury.
Now that the NDAA and its new indefinite detention provisions have been signed into law some months ago, the organization may yet be stronger than ever. The powers which it had lost in the 1970s with Hoover's passing sprang back with the Patriot Act. It remains to be seen what will be done, and how many other executives are tempted this power, mercurial as it is.