THIS MAY BE as close to the truth as we will ever know about one of the most surreal events in American history. It is a tale conceived by Franz Kafka, invested with moral dilemma by William Shakespeare. And its protagonist is living today, pumping gasoline at a garage in a Virginia suburb of Washington.

It begins like this:

"A boy sat lost on a dirt road in a jeeplike auto called a Mighty-Mite, the motor still running. It was near dusk. There was a Vietnamese fishing village on one side-- Cam Hai, a collection of coconut-frond roofs, mud, grass, bamboo, and the long, narrow fishing boats on the beach a hundred feet away.

"The boy was a pale, clean-shaven American Marine private. He wore brand- new starched and pressed fatigues, brand- new spit-shined boots, and a brand-new .45 automatic in a patent-leather holster. His Mighty-Mite was brand new, too, and he had driven out from the Headquarters Company motor pool, Third Marine Division, at Da Nang, six kilometers distant.

"The reason he had the new clothes, the new gun, the new car was that he was a division staff driver, one of those rear- echelon soldiers who taxies the brass around, and the brass like their drivers neat and clean; he was merely a chauffeur who took officers to the field and to the club. In the autumn of 1965 there was no official air of desperation in Vietnam, no feeling of despair. It was September 18 . . .

"The job was simple: 'Pick up a Marine lieutenant from a reconnaissance company near Marble Mountain'. . ."

By nightfall the boy, a high school dropout who had been abandoned as a child by mother and father, was destined for the longest recorded incarceration of an American-held prisoner of war. Barely 19 and only 12 days away from leaving Vietnam for home, U.S. Marine Pfc. Robert Russell Garwood was shot, captured and stripped of his clothing by a tatterdemalion band of Viet Cong. For the next 14 years he was held in around a dozen Vietnamese prison camps. Six years after the U.S.-Vietnam agreement in Paris securing the release of "all" (some 600) American prisoners held by the Vietnamese, Garwood turned up like a specter from a nightmare. While on a blackmarket trading mission for his concentration-camp guards in January, 1979, he managed to slip a note to an English- speaking Finnish employe of the World Bank he saw in a European bar in Hanoi.

Within a few days Robert Garwood became a media event, an inexplicable puzzle, and a political embarrassment to the U.S. government. Officially there were no Americans held prisoner in Vietnam, but thousands remained missing in action. Garwood was also once again on the edge of an abyss.

He was by all accounts a human shell extracted of his young manhood. Frail and with sunken eyes, frightened and speaking pidgin English with a Vietnamese accent, squatting instead of sitting, he was a candidate for massive psychotherapy. He had skipped an era and become a clinical phenomenon. Instead, the Marine Corps, which had renewed his enlistment without his consent and which today still refuses to pay his $150,000 back pay, charged him with a host of military crimes. They included desertion, physical abuse of fellow prisoners in Vietnam, bearing arms on behalf of the Viet Cong, soliciting Americans to surrender with a bullhorn, and crossing over to the enemy.

In February of 1980 Robert Garwood was found guilty of only the minor charges against him--collaboration with the enemy and striking a fellow prisoner. He had faced the possibility of a firing squad or life imprisonment. He was reduced in rank and given a dishonorable discharge. Garwood never took the stand in his own defense. His lawyers came and went, fought with one another, and finally chose a plea of not guilty by reason of insanity. It didn't work.

Nevertheless, as the trial neared conclusion it became clear that absurdity or madness might triumph. Dozens of previous U.S. prisoners of war in Vietnam had been pardoned for military violations ranging from signing fake confessions to broadcasting propaganda and making models of U.S. aircraft for the guidance of Vietnamese spotters. Even Jeremiah Denton "confessed" under torture. After all, this was the war in which Americans officiated at My Lai and starved the enemy by poisoning the earth with Agent Orange, the war in which North Vietnamese military nurses used coconut milk for blood transfusions because there was no plasma. It was time to drop the Garwood mess as gently as possible. One of the longest, most costly, most complex court-martials in military history ended in a whimper, not a bang.

The legal proceedings are recorded, and they make up about a fourth of this beautifully sorrowful book by Duncan Spencer and Winston Groom. What hasn't been recorded until Conversations With the Enemy is Garwood's account of those 14 lost years. Until the end of his court-martial, anything he said, including exchanges with a psychiatrist, could be subpoenaed as evidence against him.

Now we have Garwood's story. I believe most of it. So do Groom and Spencer, both former reporters of The Washington Star, both authors of other books, and Groom, a former officer in the U.S. Army in Vietnam. They have spent more than two years talking to Robert Garwood and making order out of what he told them.

Garwood's lost 14 years will have references in reality for Americans once imprisoned in Korea and Vietnam. For the rest of us the references are in literature --Kafka's "In the Penal Colony" or Alexander Solzhenitsyn's The Gulag Archipelago.

He survived in a succession of prison camps by becoming a creature of the jungle. The Vietnamese led a subhuman existence. His was that of an animal. He learned to eat insects, leaves, roots, frogs, rats, and snakes. His weight dropped from 180 to around 120 pounds. His captors fed him two or three cups a day of vermin-infested rice covered with fish broth. He was beaten, tortured, and forced to watch a South Vietnamese prisoner kill himself in a game of Russian roulette.

When first captured he went without treatment until his wounded arm swelled to balloon size and rotten flesh dropped away. He could see through the hole in it.

There was almost no food or medical care, and at the start, no communication. Almost no one could speak English.

Twice he tried to escape. Once his punishment was to be placed in stocks for a week, lying in the jungle night and day without cover. Another time his punishment was to be placed in a seven-foot- square hole in the earth, where he lived in the mire of his own urine and feces. Once he was forced to dig a fish pond with a shovel and a bucket. It took almost a year. An American bomb almost killed him.

He saw his two best friends die of starvation and beating by their captors. One, Capt. William F. Eisenbraun, may have saved Garwood's life by helping him to learn to speak Vietnamese. The other, Russell Grissett, a Marine corporal, befriended Garwood when he was ostracized by Americans because the Vietnamese had made him their interpreter- lackey and moved him to a separate hooch. Grissett was beaten to death after he and others killed and ate the camp commander's cat. It was at this time that Garwood hit another prisoner for letting Grissett become the fall guy.

In the words of Spencer and Groom Robert Garwood's story carries a slightly different version of events surrounding nearly every charge brought against him at the court-martial. He was an interpreter, not an interrogator. He carried unloaded weapons for the guards on food- foraging trips because they told him to. He shared stolen food with his fellow prisoners rather than kept larger portions for himself. He was forced to eat his rice in the cook's kitchen and sleep in a separate hooch from the other Americans because his captors believed his knowledge of Vietnamese made him a potential leader of escapes. He was, by the way, the only U.S. prisoner among the some-600 repatriated who had been able to learn the language, yet he was said to have a high-school I.Q. of 85.

"The one sure thing is that Garwood was different from the other surviving inmates, and that in fact he did some, if not most, of the things he was accused of," Spencer and Groom write near the end of their book. "The question boils down to why."

A page later Garwood answers the question in terms of survival:

"I think now that I could have done more for the others. I regret that. . . . Well, there were fifteen or sixteen guys in that camp and twelve of them are dead now. I did the best I could."

The question remains whether Garwood was in fact a prisoner of the Vietnamese until 1979, and if so, why?

Groom and Spencer believe he was. The reasons are both complicated and simple, but supported by evidence that Garwood was given electro-convulsive shock treatments by his captors to erase his memory before he left Hanoi. He knew too much.

At the start the Vietnamese believed that Garwood-- in his spiffy uniform, with his new gun and shiny holster, with his new automobile--had to be someone very important. He was a prize. They had never taken anyone so well got up. Their eventual interrogation of him suggested this. Then when Garwood learned their language rather quickly, they became convinced.

By the time Vietnamese authorities discovered they had an ordinary reluctant warrior, Garwood was lost in the bureaucracy, shuffled from camp to camp, and had become a possible source of embarrassment. He was compliant, harmless, and was good at tinkering with radios and captured American trucks. Had they thought he could ever make contact with the outside they simply would have killed him.

And what can we take from this wrenching account of a socially marginal boy from central Indiana robbed of his youth in Vietnam and pilloried at home? Another sense of why war is evil and corrupts everyone who makes it.

Conversations With the Enemy is a testament to everything dark, everything wondrous about human beings. We owe Duncan Spencer and Winston Groom our abiding gratitude for writing it.