THE RELEASE of Patty Hearst and her subsequent marriage may not serve this interesting book well; people may be finished with the whole business, may not want to read a very long day-by-day account of the trial, or any more about that time in the closet, or about F. Lee Bailey. Now that Hearst is out, the ugly implications of the legal behavior, like the ugly implications of public sentiment at the time, can conveniently be forgotten until some future occasion for public vindictiveness and private opportunism. The principal interest of Alexander's account lies in its detailed presentation of these aspects, but it touches as well on other matters that close followers of the case will have wondered about - why did the Hearsts hire Bailey, a flamboyant lawyer associated in the public mind more with flashy criminals than with dignified victims? Why did the government decide to prosecute a young kidnap victim? What was the SLA really like?

Shana Alexander daily attended the trial and talked to many involved people - the Hearst family, the legal staffs of both sides, the many psychiatrists and other expert witnesses. Each character is described vividly - perhaps a bit too vividly: "Anthony Shepard, the young caramel-colored man on the witness stand, wears a coppery Afro, a Fu Manchu mustache, a short-sleeved shirt that displays his muscles, and a tough-guy swagger. He was the clerk at Mel's, and he is studying to be cop."

What merges is a kind of soap-opera drama of rivalrous lawyer and doctors, and Alexander herself, presented as one of the characters, attempting to account for her strong emotional involvement. Alexander does this in terms of her own problems as the mother of a daughter whom she could imagine acting in some ways as Hearst had done, and as a citizen of the America which produced this odd case. She presents her own reactions and reflections in detail, and some valuable conclusions.

In the most interesting section of the book, "Closing Reflections," she talks to psychiatrists Joel Fort and Jolyon West (who had testified for the prosecution and defense respectively), prosecuting attorney David Bancroft, defense attorney Albert Johnson, Charles Garry from the sidelines, and members of the jury. The weird divergence of views, the projections of personal hangups, is startling. From the left, Garry believes that Hearst was "a cold, calculating bitch," who "got in with a gang of thieves and she became just like them." "Spooky psychiatrist" Joel Fort believes that "Patty was eager for sex because she was a sexually active girl and had been so at an early age." Alexander herself comes to believe that "Patty had been brain-washed. She had undergone a pseudoconversion, brought about through coercive persuasion, which resulted in role identification that after her capture did not sustain." This was the essence of the defense case, which most trial-watchers thought ill-judged.

Some interesting light is shed on the jury, whose seeming witlessness is to an extend explained by Alexander's revelations about the way they were treated - incarcerated more cruelly, perhaps, than Hearst herself, for whom, as the occasion of their misery, they can hardly have helped but conceive animosity: "They lived for sixty-six days without radios, television, newspapers, or magazines in single rooms equipped with alarms that rang if the door was opened after ten o'clock at night. Until the knock came at six or six-thirty the next morning, each one was entirely alone . . . Al juror could either eat alone in his room or go to a restaurant with the group. But since all sixteen had to eat together, it was difficult to avoid people one didn't like. The two drinks one was allowed before dinner were insufficient to relieve the tensions of the day . . . Golf, jogging, and most other customary recreations were impossible because each juror would have required his own marshall."

And much more.

The whole book is an elaborate answer to the question it raises: Why did this case come to trial at all? Alexander's analysis is valuable: "Who makes this determination that 'the American public demands vengeance'? . . . There are only persons and pressure groups and professional interests that - for reasons of self-interest - presume to speak in the public's name. These people can be lawyers, politicians, psychiatrists, family member, or press. In the Hearst case they all spoke. . . . An 'American public' demanding vengeance, or indeed, demanding anything else simply does not exist.

If this trial was a "travesty," how can future travesties be avoided? Alexander feels that one way would be to bar pretrial publicity by doctors and attorneys, as is done in England. Some remarks made to her by Jolyon West stand out as the burden of the whole account: "Before the trial I had faith in the fairness of our judicial system. I had a deep-seated belief that the truth will come out and that fair-minded people, if they're faced with the truth will know it when they hear it. . . . This trial was the most disillusioning thing that ever happened to me. I mean the behavior of the government."

He concludes that "when you change the number-one value from fair play to winning, you go beyond duty." Despite its breezy presentation, this detailed portrait of a legal system devoid of values is really horrifying. CAPTION: Picture, Patricia Hearst (1976), AP