IN The Breaks of the Game David Halberstam investigated the gritty, ghetto- based world of professional basketball, the jazziest athletic enterprise we've yet developed. In The Amateurs he moves to the other end of the scale, examining what passes in America for gentleman-athletes. Halberstam's subjects compete at the very highest level in rowing, "an anomaly, an encapsulated nineteenth-century world in the hyped-up twentieth-century world of commercialized sports." The battle is for the right to represent the United States in men's single sculls in the 1984 Olympics. One seat is available; four exceptional but generally unknown athletes, simon-pure amateurs, are competing for it.

Amateurism, invented by the British to avoid the mingling of sweat among social classes, has been a dead issue since the first stadium seat was rented for cash. But rowing, virtually spectator-proof, never got the word; it survives, even thrives, supported only by its own addicted competitors. Halberstam, a former oarsman himself, is transfixed by the sport's fierce grip.

"Those who competed at this level did so with demonic passion. Yet there was no overt financial reward at the end, nor indeed was there even any covert financial reward, a brokerage house wanting and giving special privilege to the famed amateur. Yet the athletes were almost always the children of the upper middle class, privileged, affluent, a group that in this society did not readily seek hardship. One could understand the son of a ghetto family playing in the schoolyard for six hours a day hoping that basketball was a ticket out of the slum; it was hard to understand the son of Beacon Hill spending so much time and subjecting himself to so much pain to attain an honor that no one even understood. Perhaps in our society the true madness in the search for excellence is left for the amateur."

Halberstam's concern is not economics but passion, true madness. The complexities of rowing as an athletic task, of its structure as an athletic task, of its structure as an international sport, are only sketched in passing. The Amateurs is not about rowing but about the four rowers: Tiff Wood, the favorite -- Beacon Hill, Harvard crew, legendarily tolerant of pain, a bronze medalist in the World Championships; John Biglow -- Yale, "powerful, relentless, indefatigable," also a bronze medalist; Joe Bouscaren -- Yale, the most abrasive, the smallest but the fiercest trainer and the best technician; Brad Lewis -- Westerner, outsider, mystic. Add a fifth character: Harry Parker, enigmatic Harvard coach, acknowledged Zen master of rowing, for these Olympic games demoted from coaching the glamorous eight-oared shells to handling the lowly, and quirky, scullers.

"Swing" is the oarsman's term for that moment when all eight oars approach perfect synch, the boat leaps and drives, the sum is greater than the parts. It is the sensation that makes athletes fall in love with crew. In the single sculls, however, cooperation is out, purest ego is in. "You could be on a championship eight which won all its races," says Tiff Wood, "but you might only be the fiftieth-best oarsman in the country. But the single sculler is the best, and everyone in the world of rowing knows it."

What John Biglow says he likes most about swing is that "it allowed you to trust the other men in the boat. A boat did not have swing unless everyone was putting out in exact measure, and because of that, and only because of that, there was the possibility of true trust among the oarsmen." Trust is a problem, particularly in the matter of effort. What makes a sculler, or any other solo athlete, is insistence on full responsibility for one's athletic fate -- no trust required. And level of effort is exactly what obsesses these individuals, in training as well as racing. Who is making how much effort? When in the race, when in the training program? How can I make more? Halberstam follows his athletes through workouts, racing camps, early-season regattas, through the torturous ins and outs of the elimination process. They work as hard as less patrician athletes, but they are more articulate about it. They are the princes of our society, for whom confidence is supposedly a birthright; they fail, which is the birthright of athletes. Halberstam collects their thoughts about these things. Building character is never mentioned; neither, really, is pain.

In his usual fashion Halberstam interviews everyone, triangulates every opinion, gets incisive insights and hard judgments even from the oarsmen's mothers. The result is pure reporting on a level undream t of elsewhere in sports. It is also an extended rumination on the limits of human effort, on true madness in the search for excellence. What further sets it apart from other writing about sports is that most of it is presented from the viewpoint of members of our society whom circumstance s have blesse d with unlimited expectations. Thus in a peculiar way it tells what our best and brightest -- Halberstam's larger obsession -- are up to these days. Here is how those minds work. This is one way, anyway, that they learn their expectations are not unlimited after all.