FROM A LITERARY standpoint, the Sacco and Vanzetti case was the American crime of the century. No other criminal case has generated so many works of substance and style.

This concise, clearly written and cogently argued book may bring to a close six decades of controversy. It is the product of an unusual collaboration. William Young was a successful rare book and art dealer in Massachusetts who researched the case as an intellectual avocation. He wrote a rough draft of a manuscript setting forth his researches and conclusions. Shortly before he died in 1980, he turned the manuscript over to his friend David E. Kaiser, a young professional historian on the faculty of Carnegie-Mellon University, who did additional research and rewrote the manuscript in publishable form.

The classic account arguing for the innocence of the two defendants is The Sacco-Vanzetti Case published in 1931 by Osmond K. Fraenkel, a distinguished New York lawyer and civil libertarian. Francis Russell's Tragedy in Dedham in 1962 is an equally comprehensive and brilliantly written work which concludes that Nicola Sacco was guilty and Bartolomeo Vanzetti innocent but peripherally involved. For readers coming fresh to the controversy, the Young-Kaiser book can be understood and enjoyed by itself as an exquisite piece of detective work. For connoisseurs of the case, it can be read as a series of fascinating footnotes and amplifications of Fraenkel and a rebuttal of Russell.

Vanzetti, a fish peddler, and Sacco, a shoe worker, were arrested in Massachusetts in May 1920. Vanzetti was immediately brought to trial and convicted of an attempted payroll robbery in Bridgewater the previous Christmas Eve. Almost a year latter in May 1921, he and Sacco were brought to trial for the murder of two guards in the successful robbery of a $15,000 payroll in the nearby town of South Braintree which had occurred in April 1920. They were convicted and eventually received mandatory death sentences. At both trials, the prosecution was under the supervision of District Attorney Frederick Katzmann and Judge Webster Thayer presided.

As immigrants and as members of an anarchist group that believed in violence, the two defendants were natural targets of suspicion at a time when the Justice Department under Attorney General A. Mitchell Palmer was conducting an extensive campaign against communists and other radicals and deporting large numbers of aliens.

Fred Moore, a radical lawyer from the West Coast, was brought to Massachusetts by anarchists to head the defense. Using the press skillfully, he made the case an international cause c,el his flamboyant style and aggressive tactics may have harmed his clients with the jury and with local public opinion. Vigorous investigations directed by Moore and later by his successor as chief defense counsel, William G. Thompson, developed much new evidence and led to several motions for a new trial. Judge Thayer denied them all.

The controversy reached a wide audience when Felix Frankfurter, then a professor at the Harvard Law School, wrote an article in The Atlantic Monthly in March 1927 denouncing the trial and the standard of justice prevailing in Massachusetts. The local establishment rose to the challenge. Governor Alvan T. Fuller appointed the presidents of Harvard and Massachusetts Institute of Technology and a well-known Boston judge to review the case. The Lowell Committee, named after President A. Lawrence Lowell of Harvard, affirmed the conviction. Sacco and Vanzetti were executed on August 23, 1927, as thousands demonstrated in protest in Boston and in the major cities of Europe. In that comparatively innocent and hopeful age before Hitler's holocaust and Stalin's gulag and South African apartheid, people were still capable of outrage over the deaths of two individuals.

YOUNG AND KAISER show that the protests were well-founded. There were so many grounds for reasonable doubt that the death penalty was clearly unjustified and their convictions should have been set aside in favor of a new trial. In the first trial in which Vanzetti was the lone defendant, witnesses gave testimony in court which varied considerably from what the same persons had told Pinkerton detectives investigating the case several months earlier before anyone had been arrested. Judge Thayer revealed his prejudice against the defendant in the way in which he managed the sentencing. He filed the conviction on the graver charge of assault with intent to kill, thereby setting it aside and making it impossible to appeal. On the lesser charge of assault with intent to rob, he then sentenced Vanzetti, a first offender, to the extraordinarily severe term of 12 to 15 years, by far the harshest sentence he handed down during those years. It contrasts with sentences of as short as six months and as long as three years that he had imposed in similar cases. Inescapably, one has to infer that Vanzetti's anarchism was a factor in the mind of this conservative Yankee.

The trial of Vanzetti and Sacco for the murder of the two guards in the successful holdup was also deeply flawed. Most of the witnesses to the crime could not identify either defendant. Those who did identify them gave conflicting accounts in their original police interviews, to the grand jury, and at the trial. Some were badgered by the district attorney into being much firmer and more specific than they had initially been.

The only physical evidence linking Vanzetti with the double murder was a revolver found on him at the time of his arrest. The prosecution successfully planted in the minds of the jurors the belief that this was a gun belonging to one of the two murdered guards. In reality, state police records made available in 1977 show that the police had traced the victim's gun and knew that it had a different calibre and a different manufacturer's number than the gun found on Vanzetti. "The prosecution successfully concealed their knowledge from the defense and ultimately from the Lowell Committee. . . . The Prosecution sent Vanzetti to the electric chair on evidence they knew to be false."

The damning evidence against Sacco came to be known as Bullet III. It was one of four bullets taken from the body of one of the murdered guards. Two firearms experts testified at the trial that this bullet probably had been fired through the Colt .32 automatic found on Sacco on the night of his arrest.

"By modern standards none of these opinions was worth very much. The comparison microscope, which enables experts to make such judgments with a high degree of certainty, had not yet been developed, and forensic ballistics as practiced in 1921 was far from an exact science," the authors observe.

When writing his book in 1961, Francis Russell arranged for two new experts to test the weapon and the bullet using a comparison microscope. They confirmed that this bullet had been fired from Sacco's gun while all other bullets in the case came another unknown weapon. How Young and Kaiser refute this seemingly conclusive evidence is the high point of their book.

"The puzzle of the bullets can be solved by reconstructing the actual shooting with the help of the eyewitness testimony and the testimony of the autopsy surgeons," they write.

The guard was killed by one of the bandits who stood over him and fired at least two shots at point-blank range. "The bullet III introduced in evidence can only be genuine if the bandit who fired it did not hit Berardelli (the guard) with any other shots."

The authors conclude that the Bullet III which was introduced as evidence and which came from Sacco's gun had been substituted for one of the bullets that the surgeon removed from the dead man's body. The authors hypothesize that the switch was made by one of the two policemen who investigated the case for the district attorney. An attempt to have their hypothesis confirmed by modern scientific instruments proved inconclusive. Nevertheless, their explanation is consistent with the testimony of witnesses and the autopsy, while the theory that Sacco fired a single shot while someone else fired all the other bullets is inconsistent.

Postmortem is cool and unemotional. It sets forth but does not dwell upon the political atmopsphere surrounding the case. On one level, it can be read like a detective story or as an intellectual puzzle. On another, it is a psychological drama involving a prejudiced judge, a crafty district attorney, a defense lawyer who overplayed his hand, and slovenly policemen who cut corners when the facts did not fit their presuppositions. On the deepest level, this book like its several impressive predecessors is a testament to the enduring American passion to learn the truth and to do justice, even if posthumously.