NEW YORK -- It was supposed to be finished in 1985. It was supposed to be half as long as it turned out to be. It was expected to enter the nether reaches of the bestseller lists, with a little luck, and then start the difficult climb upward; it would take time, presumably, to persuade readers to curl up on a winter's eve with a comprehensive history of the oil industry.

But author Daniel Yergin, immersed in the breadth and romance of his subject, blew his deadline. Blew several deadlines, in fact. Turned in the bulk of his hefty manuscript last spring and finished the epilogue five days before the invasion of Kuwait, whereupon the topic of petroleum suddenly grew considerably more compelling.

With inadvertently exquisite timing, Yergin's "The Prize: The Epic Quest for Oil, Money and Power" has gone through seven printings since early December and has landed on the bestseller lists with an 800-page whoompf: It makes its debut on tomorrow's New York Times list at No. 2 and will top both the Times and the Washington Post nonfiction lists next Sunday.

"The Prize" is not the only book to benefit from intense public interest in the Persian Gulf, of course, but it probably is the only one to have consumed seven years of research and writing. While Yergin was interviewing dozens of sources from William Colby to T. Boone Pickens, a researcher in London was rummaging through the archives of the Public Records Office and another was on the case at Harvard's Widener Library. At least, as Yergin remembers his impatient editor pointing out, "no one could accuse me of writing an instant book."

For all the footnotes and its daunting 25-page bibliography, Yergin has written a surprisingly engaging one, though. The 131 years since "Colonel" Edwin Drake struck oil in Pennsylvania became a narrative drama featuring a cast of outsize players -- scheming wildcatters and capitalist moguls, desert kings and serendipitous geologists, statesmen and muckrakers and OPEC ministers. A reader can almost understand why half a dozen television producers have contacted Yergin about the possibilities of a miniseries (though the saga lacks sufficient sex). Reviews of "The Prize" have been nearly uniformly admiring.

It probably helped that before Yergin became the unusual hyphenate that he is, a historian-businessman, before he was an earlier and more common hyphenate, an author-academic, he was a magazine journalist and "one of the nation's champion op-ed writers." In fact, even before that, he was an English literature major, studying Dickens and Thackeray at Yale. He found early on that "if I wasn't writing a book, something was missing... . That's how I define myself."

His first, "Shattered Peace," a history of the origins of the Cold War, began life as his Cambridge University doctoral thesis. His second was the best-selling "Energy Future: Report of the Energy Project at the Harvard Business School," which he edited with B-school professor Robert Stobaugh. With the knack for synchronicity that's currently standing Yergin in such good stead, the conservation-minded volume was completed a year late and hit bookstores in 1979 -- just as gasoline lines were forming again.

It made Yergin prominent in energy circles. Oil interests weren't fond of his arguments, recalls Herb Schmertz, then Mobil's take-no-prisoners superflack, now head of an independent public relations firm. "The scenarios he spun out were not consistent with the views of those responsible for providing energy," says Schmertz, who still believes that conservation is "simply a euphemism for reducing your standard of living." Among citizen groups and think tank sorts, though, "Energy Future" was respectfully received.

"The Prize," however, is a different species of success: An eighth printing, now underway, will bring the number of books in print to more than 175,000. Copies of the far-from-instant tome are stacked on a conference table here at Simon and Schuster so that the author can inscribe them for grateful booksellers and distributors. It took a crash publishing effort to get a history of oil into bookstores while "No Blood for Oil" anti-war protesters were marching in America's streets, but it has paid off.

Yergin, who lives in Northwest Washington with his wife (Georgetown professor Angela Stent) and their two preschoolers, had gone to England last summer, "to quietly read my galleys." Like the rest of the population, he woke up on Aug. 2 to learn that "the new post-Cold War situation had been rudely interrupted." But the fact is, the 43-year-old author says, he didn't have to make major revisions in his text when Saddam Hussein made his move.

A year and a half ago, he says, "I got this really strong sense: This oil market was beginning to look like the '70s." With U.S. oil imports up, demand outstripping forecasts, and low prices discouraging investment, the situation "seemed to be heading for the crisis zone," Yergin thought.

At the same time, "there'd been enough signals of Iraq's changing status versus the rest of the world." Yergin had already rewritten those sections of the book pertaining to Iraq and its politics, highlighting Saddam's emergence. Yergin concedes that he thought Saddam likely to content himself with seizing the Kuwaiti oil field and islands to which he had laid claim. "No one would be able to spell them anyway and the world would hardly notice," Yergin says.

Instead, war. Yergin doesn't want to say it's about oil, because "wars don't happen for one reason. It's neater if you can say it's about one thing, but it's about an interrelated series of things -- the balance of power, nuclear and chemical weapons, the post-Cold War order. But oil is certainly very central."

He doesn't want to discuss his own feelings about the war much, either. Yergin's happy enough to reflect on the strong sense of de'ja` vu it triggers for anyone who's been immersed in the geopolitical history of oil in the Middle East. Pan-Arab nationalism, complacent Western consumers, here it all comes again. "I find so many echoes of the last 30 or 40 years," says Yergin, who thinks the invasion of Kuwait could have changed the balance of power in the world. "It really is a pity that people don't know their history."

But ask him whether he thinks the Bush administration response was warranted or will prove efficacious, and his discomfort is evident. He wants to be "an analyst and not an advocate. Part of what I try to be is objective and balanced."

This caution stems in part from Yergin's other profession. He's long had "an entrepreneurial bug," and in 1982, the same year he embarked on "The Prize," he and two colleagues founded a business, an international energy consulting firm called Cambridge Energy Research Associates. He won't divulge the company's revenues or its client roster, but it has grown to employ 60 people, plus 20 part-time associates, in its Harvard Square home office and in branches in Paris, Oslo and San Francisco and, most recently, on Connecticut Avenue.

Cambridge Energy's clients -- banks, pension fund managers, airlines, automakers, oil producers, utilities -- subscribe to various forecasts and reports on energy markets. Such clients' interests do not always coincide, and Yergin treads carefully so that "people on both sides of issues can read our work and find it useful."

He doesn't care, for instance, to blast the Bush administration, which has yet to unveil its national energy strategy. By now, "I would have expected more discussion," Yergin says mildly, though he does note (as have other commentators) that energy was awarded but a single line in the State of the Union address. "Everywhere I go, the question is 'Do we have an energy policy? Why not?' It means something different in Houston than in San Francisco, 'energy policy,' but the question comes up."

As for his own notions of what an energy policy ought to be, Yergin says circumspectly that in a forthcoming piece for Newsweek he'll "come close to advocating a higher gas tax," among other things. Close to? "We should overcome our phobia of discussing a gasoline tax," he says finally, taking a position in favor of. In inflation-adjusted terms, he notes, gasoline is still cheap in the United States; stimulating conservation by making gas more expensive "is a sensible thing to do. But it doesn't have the drama of a Project Independence" -- which was Nixon's ballyhooed and unfulfilled energy project -- "or a huge synfuels program" -- which was Carter's.

Some who knew him from the energy policy battles of the '70s are a bit disappointed that the analytic Yergin won't step into a more hortatory role. "There's really nobody you think of, with all the conservation and environmental organizations ... that has come to the fore as a leader and a public educator, a Ralph Nader for the field," says James Flug, who once led the consumer group Energy Action and is now a Washington attorney involved in energy cases. "If {Yergin} has automobile companies as clients, he can't really take a forthright stand on mileage standards. If he's got utilities, then his position on lowest-cost strategies may be constrained."

Still, Flug and another veteran of the Washington policy wars, Edwin Rothschild, now energy policy director of Citizen Action, can only applaud the prospect of tens of thousands of Americans reading about oil and energy. Yergin, says Rothschild, has done "a basically good job of going back and giving readers a sense of how the industry, key players and governments have worked, together or at cross-purposes, to bring us to where we are today."

For the record, "Energy Future" was "right on target" in predicting that the United States could be 30 to 40 percent more energy-efficient, Yergin says. More than a decade later, the country is 30 percent more efficient, he says. "The American people get a bum rap. We did a pretty good job on energy conservation. But it has flattened out."

Where he and his co-writers erred, he says, was in being "way too optimistic" about renewable energy technologies like solar power and how quickly they would become available and practicable. He still thinks they can eventually "play a more important role." But as he says in "The Prize," in the epilogue's very last line, "Ours truly remains the age of oil."

Yergin sees oil -- the quest for it, the price and supply of it, the strategic importance of it -- as a major reason for everything from the attack on Pearl Harbor to the rise of fast food. He confesses, now that he's a businessman himself, to being particularly "fascinated by the tycoons. By the willpower, the risk-taking."

In fact, Yergin found oil such an intoxicating subject that he supposes one or two of his critics may be right when they suggest that he's written "an oilcentric history" (his own phrase) of the 20th century.

The mid-'80s oil glut may have temporarily lulled the West into forgetting about energy issues, but history tends to provide reminders. "In the spring of 1990, people were saying oil doesn't matter," says Yergin, who testified at a little-noticed Senate hearing last March about the risks of the tightening supply. "No one was there," he recalls, "but a senator predicted that within the decade we'd all be back in the hearing room and it would be full."

It took a mere seven months. In October, with U.S. troops in Saudi Arabia and more on the way, Yergin testified at another Senate hearing on the same subject in the same hearing room. "It was filled," he says.