SECRECY AND POWER The Life of J. Edgar Hoover By Richard Gid Powers Free Press. 624 pp. $27.95

NEUTRALITY ABOUT J. Edgar Hoover is difficult. Many of those who lived through his years on center stage are convinced he was the devil incarnate, an unscrupulous man who wielded enormous power with reckless abandon. Many others, however, are convinced he was an avenging angel whose assaults on criminals and subversives kept America free.

This full-dress biography of Hoover left me thinking each view is half right. He was, at times, everything his critics said -- dishonest, malicious, prejudiced, petty and pompous. He was also, at times, brilliant, honest, loyal to a fault and, of all things, sympathetic to civil liberties.

Richard Gid Powers, a professor of history at the City University of New York's College of Staten Island, may have caught the essence of this strange man who ran the Federal Bureau of Investigation for 48 years before his death in 1972. Powers has put together a stunning tale of the rise and fall of an essentially tragic figure, a man of great abilities who at the end, isolated and alone, did not understand the country he had spent a lifetime protecting.

His book is rich in detail (sometimes too rich) and sparse but sharp in commentary. It impartially documents both triumphs and disasters. Hoover did build a magnificant investigative agency that stopped the crime wave of the '30s, eliminated sabotage during World War II, and broke the American Communist Party and the Ku Klux Klan. That he sometimes lied, or stretched and broke the law, is also part of the tale, as are the decisions of his last decade which almost destroyed his beloved FBI.

Powers' thesis is two-pronged. The first is that most of the things Hoover did, good or bad, he did for the purpose of protecting the America he loved. The second is that his America was always the America of his youth -- defined as the middle-class Washington society into which he was born in 1895. In his America, family and church were prominent, proper behavior was essential, obedience to authority was expected, love of country was paramount and blacks were an inferior servant class. (There were five black FBI agents in 1961, all providing essentially personal services to the director).

This thesis goes a long way towards explaining -- explaining, not justifying -- the way Hoover responded to most of the major controversies he confronted.

Those were many. They began with the internment of German immigrants during Wold War I; Hoover handled the paperwork and, interestingly, was more sympathetic to the immigrants than were his superiors. They ended just six weeks before Watergate, which he may have provoked by refusing to have the FBI undertake all the spying the Nixon White House wanted. In between were the Red Scare of the '20s, the crime wave of '30s, the Nazis, the Communists, the civil rights movement and the peace movement of the '60s.

HOOVER PERCEIVED in each of these episodes a threat to the America he understood. He could not accept the possibility that good Americans might disagree with him. Powers' recital of the way Hoover handled these threats demonstrates how easy it was for the FBI to move from investigating organizations to trying to destroy them. It was these latter efforts, particularly against the civil rights and peace movements, that almost destroyed the FBI. Yet some of the same tactics had been used, and publicly acclaimed, against the Nazis, the Klan and the Communists.

Take, for instance, Hoover's assault on the civil rights movement. Its goal was to change the America he was protecting, an America in which blacks were simple, uneducated people who knew their place. Since such folk were incapable of organizing and sustaining so large an effort, an outside force had to be leading them. Hoover could never prove that, but he kept trying. He eventually unreashed an unscrupulous assault on the Rev. Martin Luther King Jr., trying to get King to kill himself because he believed King ignored the threat of communism and was morally unfit to be a leader of Americans.

Powers does not blame Hoover for all the FBI's misdeeds. He parcels blame out, some to various presidents and some, contrary to other versions, to William Sullivan who ran the anti-civil rights and anti-peace programs.

This book is rich in tidbits:

Of the 10 presidents he served, Hoover was closest to Roosevelt and Johnson. It was Roosevelt who steered the FBI into investigating political subversion, and it was Johnson who pushed Hoover into greater efforts against the wilder black power advocates and anti-war demonstrators.

Hoover provided political intelligence to almost every president. He investigated the Navy League when it opposed President Hoover. He sent agents to the Democratic National Convention in 1964 to keep President Johnson informed of what dissident delegates were planning.

On the other hand, Hoover opposed the internment of Japanese-Americans during World War II, telling his bureu chief in San Francisco that "the Army was getting a bit hysterical," and describing in 1943 the evacuation as being "extremely unfortunate."

If you cherish a simplistic view of J. Edgar Hoover, be warned: this book will challenge it. It is essential reading for anyone who wants to understand the relationship between the government and its opponents, criminal or political, from World War I to Vietnam. :: James E. Clayton, a former associate editor of The Washington Post, covered the Department of Justice in the 1960s.