Most portraits of J. Edgar Hoover and "his" FBI offer the subliminal impression that in Hoover we had a peculiarly American hybrid of Ivan the Terrible and the head file clerk at the Circumlocution Office in Dickens' "Little Dorrit," the ultimate bureaucracy where they really knew how to keep important things from happening. He maintained no Gulag, of course, and had no Siberia to send deviant agents to; but summary powers of transfer and demotion, freely exercised, often served the same intimidating purposes.

This entertaining and informative book is essentially the self-told story of Neil J. Welch, a tough Nebraskan who rose to become the FBI's "top field agent," that is, special agent in charge of the New York office with one crucial tour of duty in Washington. His coauthor is David W. Marston, the boyish Philadelphia prosecutor whose clash with the Carter administration made brief headlines in 1977.

Iconoclastic to a point, this book is not quite in the conventional anti-Hoover mold. Indeed, it pays the usual obeisances to Hoover's avoidance of politics and corruption (the obvious kinds, anyway) and his political nimbleness. Otherwise, it is an exercise in limited enthusiasm.

Of course, it concedes to Hoover's credit certain solid accomplishments. Appointed by Harlan F. Stone in 1924, Hoover cleaned up a scandal-ridden agency and kept it scandal-free. The investigative techniques he developed in the 1930s made kidnaping, once epidemic, a relative rarity, and showed the famous "gangsters" of that day that they were not invulnerble. Welch is impressed, also, with the skill Hoover showed in investigating the Mississippi civil rights atrocities in the early 1960s, once challenged to enter the scene.

The basic problem with Hoover, as Welch sees it, is that he lingered much too long, and certain outdated obsessions (auto theft, for instance) lingered with him. Lyndon Johnson, Hoover's longtime Washington neighbor, committed the first error. He waived, in Hoover's favor, the mandatory federal retirement age. Soon the director had become immovable, although Welch neither confirms nor refutes the old rumor that it was the dirt in Hoover's private files that terrified presidents (with the usual exception of Harry Truman).

Even conceding Hoover's virtues, Welch's argument is that bureaucratic rigidities severely limited the scope and effect of FBI operations. There was an iron-curtain division between headquarters mandarins and agents in the field; and the former, loyal to Hoover at all costs, insisted on making all the important decisions. Crime statistics were a fetish, but a poor and misleading measure of real effectiveness. There was far too much emphasis, Welch believes, on domestic subversion (there was a time when most Communist Party cells in the United States were rumored to consist, in large measure, of FBI double agents) and much, much too little on organized crime.

Hoover's obduracy on the latter subject may be gauged, Welch suggests, by the fact that until (and even after) the great roundup of organized-crime bigwigs at Apalachin, N.Y., in 1957, Hoover refused to acknowledge the power or even existence of the Mob. Not before Robert Kennedy's attorney generalship in 1961 was an anti-crime strike force established. Even then, the initiative came from Kennedy, not Hoover, and offended Hooverian protocol in all sorts of ways. Kennedy, for instance, often worked on Saturdays and fraternized with lower-level FBI agents.

Essentially, then, this is a tale of what might be called heroic insubordination -- how Welch, working in various big-city field offices, worked out the techniques for penetrating organized crime and political corruption whose monument would be Abscam. Had Hoover known what was going on under Welch's direction, he would, we are led to believe, have stopped it cold.

It is an entertaining tale, full of fascinating anecdotes, and for the most part wittily told. There is inevitably a certain boastful air about it. Welch, who came close to being named Hoover's successor (he was the unanimous choice of a citizen's nominating commission named by Jimmy Carter) seems in many ways an admirable character.

One is given pause only by his reiteration of how he cleverly defied, evaded or bent standard procedures or regulations, all for the greater good of crime fighting. He netted some big fish in organized crime and political payoffs, always taking care to gratify the director's vanity by giving him credit. And the techniques he developed will surely continue to catch others. But I couldn't help wondering, from time to time, what would become of orderly government if every agency had an abundance of innovative, clever, inventive insubordinates like Neil Welch. Finally, I had the feeling that one is about all each agency could possibly manage, or benefit from. But every agency needs one.