Has all the names and descriptions of Hoover's time. Prominent mistakes are that it misses well known FBI files of celebrities such as Frank Sinatra, John Lennon, Mickey Mantle and (yes, it's true) the members of the Monkees musical group.
Ms. Gage also makes the mistake of obviously judging past words and events by current standards.
Further Ms. Gage devotes very little time to the JFK assassination. Were Hoover and the FBI part of that ? We all know or should know that there's more to that story.
Finally, the specific details and politics of civil rights should, perhaps, be left to history books. Easy to research but now of little consequence..