The Federal Reserve plays a major—some would say oversize—role in American life, but it is, for many citizens, a mysterious entity: Unelected officials pore over reams of data and rely on abstruse models and theories to set interest rates, regulate banks and otherwise ride shotgun for our vast and fluid economy. Should we be worried? The Fed “attracts conspiracists better than most governmental agencies,” concedes Peter Conti-Brown in “The Power and the Independence of the Federal Reserve.” To many observers, the Fed is “a dark and brooding omnipresence that can be accounted for only with nefarious explanations.” Little...