THERE IS a pioneer's intensity in David Halberstam -- a tireless will to push on, stretch out; a hunter's sense for the hidden fragility in things that claim power; an eye for seeing large cities where others only see stones. He is the author of 13 books, among them his Pulitzer Prize-winning The Best and the Brightest (1972) about the Vietnam War; The Powers That Be (1979) about the American media establishment; The Reckoning (1986), a dual history of the Ford and Nissan companies; and Summer of '49 (1990), a paean to American baseball. These are big books in every way: fat bestsellers fashioned from mountains of accumulated detail, hearty slices of big-picture America. Halberstam's latest book, The Fifties, is no less in scope. A massive cultural history of the decade, it seeks to trace the roots of our current national psyche and explain how we have become what we are today.

Born in New York City in 1934, Halberstam was the grandson of a Hassidic rabbi and the son of an itinerant army doctor. He graduated from high school in 1951 and went on to Harvard, where he became the editor of the Crimson. Upon graduation in 1955, he headed South, attracted by the issues of social conscience abrew there. As a Nashville Tennesseean reporter for four years, he covered civil-rights stories, among them the case of Emmett Till, the 14-year-old black boy who was murdered because he whistled at a white woman. Halberstam admits now that, although he reported it, he did not comprehend the historical force of that story until many years later. Not until he sat down to address it in The Fifties.

In 1960 he was recruited by the New York Times and shipped out to the Congo. Within a year he was reporting from Vietnam, writing front-page pieces that claimed the war was "on its way to becoming a first-class failure." Halberstam's pessimism led President Kennedy to approach the New York Times to ask for his recall. Halberstam stayed in Vietnam but eventually returned to the U.S. in 1964 to report on civil-rights developments in Mississippi. In 1966 he became the Times correspondent in Poland, but he was expelled shortly thereafter for writing that the communist government was a farce -- an invisible occupation without roots in Polish soil. Known by now for his inclination to write longer stories, he left the Times in l967 for Harper's magazine, where he stayed until the publication of The Best and the Brightest.

The Fifties, Halberstam says, is as close to autobiography as he will ever come. In it, he has tried to take history one step further, making players out of things and events: the mechanical cotton picker, the birth control pill, the computer, Levittown. "These were all factors of my life and times -- I could well have put them into my own story -- but I've chosen an exterior rather than an interior stance." As usual, his book is comprehensively reported: It is journalism writ large.

But already he is thinking ahead, pushing on. There is a quick book he has in mind about the Yankees and the Cardinals. And then a big one after that: "Did you ever stop to think what became of the young blacks who took part in the sit-ins in the early '60s? The kids who stood up to all the beatings? I was there. I was just a kid reporter myself. I covered them. Well, what became of those people? That's what I want to find out."