IN LATE January 1981, Joe Klein, the author of a biography of Woody Guthrie, saw a headline in a New York tabloid about a Vietnam veteran named Gary Cooper, who was killed in a shoot-out with police after going "berserk" in anger over the welcome given the Tehran Embassy hostages. In pursuit of a magazine story, Klein went to Hammond, Indiana, interviewed Cooper's family and friends, and discovered that Cooper, an unemployed ex-Marine with a history of unnecessary trouble, was at least as upset with his dwindling job prospects as he was with the reception given the hostages.

Vietnam was not the beginning of Cooper's troubles, but it almost certainly contributed to the end of them. His wife had pleaded with the police not to hurt him, saying, "He thinks he's back in Nam!" And the way Klein tells it, there is little doubt that Cooper was going through some sort of flashback. When the police shot him, he fell screaming, "I'm hit!" It was Cooper's second gunshot wound -- his first had come on his 21st birthday, in Vietnam. That time he'd been "medevacked" and awarded a Purple Heart. This time he was dead within minutes.

In Payback, Joe Klein writes about Cooper and four of the men who were with him when he was wounded during Operation Cochise, in the summer of 1967.

In a prologue with the wonderfully sardonic title, "The Summer of Love," Klein introduces each of these men as strangers he is meeting for the first time -- or in the case of Gary Cooper, a stranger he will never meet. In this prologue he also tells us a bit about himself -- he was a "foot soldier" in the antiwar movement. He then goes on to explain the situation in which the men of Charlie Company, 1st Battalion, Third Marines, found themselves in the summer of 1967. For someone who has no personal experience of war or military life, and who, before beginning this book, knew no Vietnam combat vets, Klein does a remarkable job. But he is just warming up in the prologue. The next chapter -- the only chapter devoted entirely to the war -- contains some of the most vivid, harrowing, and emotionally honest combat writing to come out of Vietnam.

Either combat is easier to understand and describe than generations of veterans realize, or Joe Klein has an incredibly accurate imagination and the omniscient empathy of a great novelist. But Payback> is not a novel. And most of it is not about the war, but rather the aftermath of the war.

THE POSTWAR Cooper is not the most sympathetic character -- but then he had no chance to defend himself to Klein. Klein seems reluctant to pass judgment on Cooper, but what emerges from the stories people who knew him told Klein is a portrait of a selfish, weak- willed, violent loser.

Bill Taylor comes off a little bit better. He drinks too much at times, has trouble with his wife, submits himself to "est" training, and ends up selling insurance. But when his wife thinks about unbalanced Vietnam vets she thinks, "He's one of them!"

Dale Szuminski -- "Ski" to his buddies in the Marines, "Mr. Rent-a-Party" to his friends back home -- is easily the most rambunctious of the five ex-Marines in Payback. After leaving the Marine Corps, he totals an awesome series of Corvettes, complicates the lives of every woman he gets next to, reads and rereads Helter Skelter, and drinks himself into Alcoholics Anonymous -- where he can't help feeling that most of those confessing in therapy had more exciting lives before they took the cure. Though an amiable fellow -- a dangerously amiable fellow -- whose survival any decent reader will celebrate, Ski seems to be stuck in the 1960s, always afraid that the party will end and he'll be sent back into the field.

John Wakefield, the Force Recon veteran who considered himself the most professional Marine in Charlie Company, doesn't seem to have done too well in civilian life and probably should have stayed in the Corps. When Klein meets him, he is overweight, morose and troubled -- but securely married and gainfully employed. He, too, had his bouts of alcoholism and despair. Taylor went through "est." Szuminski suffered through Alcoholics Anonymous. But Wakefield -- the old Recon Marine -- tops the others once again, and gets involved with Synanon. By the time Klein meets him and arranges for him to get together with some of the other men from Charlie Company, Wakefield seems a sad character who pushes counseling on his buddies and caters to Klein's preconceptions with stories of very unlikely Force Recon atrocities.

JOHN STEINER -- who was severely wounded on a second tour, after serving in Charlie Company -- is obviously Klein's favorite. Klein says that Steiner is the most gentle man he's ever known. All of the other men went back to their prewar worlds and found them changed and strangely hostile. But Steiner didn't go back to his old life -- he started a new one. He went to school and suffered the alienation that most veterans on campus felt in the late 1960s and early 1970s. He studied biology and found a job that would take him back to the woods and show him a little peace. Though his professional ambition is stunted -- a condition that seems to be very common among Vietnam combat veterans -- Steiner seems to have found some satisfaction in his civilian work. Though his colleagues occasionally find him a tad starchy and "militaristic" in his bearing, Steiner is the only one of the five who seems to have learned what he could from the war -- and then left it behind.

Only rarely does Klein indulge in shibboleths from his days as an antiwar "foot soldier," and he obviously admires the men in his book. But perhaps he has done them a disservice.

Klein denies that these men are particularly representative of those who served in Vietnam. He also denies that Payback is a book about the "plight" of Vietnam veterans. Had he changed the names and smudged the details, he could have called Payback a novel and avoided the need for this disclaimer. But Payback is nonfiction, and despite Klein's disclaimer it will be read as a book on the plight of the Vietnam veteran.

By their presence in this book, Gary Cooper and the other ex-Marines featured in Payback will inevitably end up representing the general run of Vietnam combat veterans -- at least to people like Joe Klein, who don't know many other combat vets but know these few men very well. Payback is an excellent book and will be widely read. Soon there will be thousands of strangers, all over America, knowing a lot more about Gary Cooper, Dale Szuminski, Bill Taylor, John Wakefield, and John Steiner than they have a right to know. Their privacy is gone. All their secrets are out -- or at least all the secrets Klein believed.

With the publication of Payback, all five of these men -- Klein, and the four surviving Marines -- will be subject to phone calls from brothers they never knew, combat veterans who just want to link up and talk things over. This is the sort of thing that happens to veterans who write books or appear in them. Though not a veteran, Joe Klein will get his share of calls. He has shown that he can listen.