WHEN Mohamed Atta and his four Saudi confederates commandeered a Boeing 767 and steered it into the north tower of the World Trade Center, they began a story that still consumes us nearly five years on, and one that seems, on bad days, to promise war without end.

But the events of Sept. 11, 2001, were in many ways less the start of a tale than the end of one, or at least the climax of one, begun many years before in many different precincts: in the middle-class suburbs of Cairo, in the mosques of Hamburg, in Jidda, in Islamabad, in the quiet university town of Greeley, Colo.

In its simplest terms, this is the story of how a small group of men, with a frightening mix of delusion and calculation, rose from a tormented civilization to mount a catastrophic assault on the world’s mightiest power, and how another group of men and women, convinced that such an attack was on the way, tried desperately to stop it.

What a story it is. And what a riveting tale Lawrence Wright fashions in this marvelous book. “The Looming Tower” is not just a detailed, heart-stopping account of the events leading up to 9/11, written with style and verve, and carried along by villains and heroes that only a crime novelist could dream up. It’s an education, too — though you’d never know it — a thoughtful examination of the world that produced the men who brought us 9/11, and of their progeny who bedevil us today. The portrait of John O’Neill, the driven, demon-ridden F.B.I. agent who worked so frantically to stop Osama bin Laden, only to perish in the attack on the World Trade Center, is worth the price of the book alone. “The Looming Tower” is a thriller. And it’s a tragedy, too.

IN the nearly five years since the attacks, we’ve heard oceans of commentary on the whys and how-comes and what-it-means and what’s nexts. Wright, a staff writer for The New Yorker — where portions of this book have appeared — has put his boots on the ground in the hard places, conducted the interviews and done the sleuthing. Others talked, he listened. And so he has unearthed an astonishing amount of detail about Osama bin Laden, Ayman al-Zawahiri, Mullah Muhammad Omar and all the rest of them. They come alive.

Who knew, for instance, that bin Laden, far from being a warrior-stoic fighting against the Soviet Union in Afghanistan, was actually a pathetic stick-in-the-mud who would fall ill before battle? That the combat-hardened Afghans, so tired of bin Laden’s behavior, declared him and his Arab associates “useless”? Or that he was a permissive father and indulgent husband? Or that he is only six feet tall?

More important, who knew — I sure didn’t — that bin Laden had left behind such a long trail of words? Wright has found them in books, on film, in audio recordings, in people’s notebooks and memories. This has allowed him to draw an in-depth portrait of bin Laden, and to chart his evolution from a self-conscious step-child growing up in Jidda, Saudi Arabia, to the visionary cave-dwelling madman who mimics the Holy Prophet in his most humdrum daily habits.

Wright takes the title of his book from the fourth sura of the Koran, which bin Laden repeated three times in a speech videotaped just as the hijackers were preparing to fly. The video was found later, on a computer in Hamburg.

“Wherever you are, death will find you,

Even in the looming tower.”

There is poetry, too. Here is a particularly chilling bit, found on another videotape, which bin Laden had read aloud at the wedding of his 17-year-old son, Mohammed. The celebration took place not long after a pair of Qaeda suicide bombers, riding in a tiny boat filled with explosives, nearly sank the billion-dollar guided missile destroyer Cole. At least with regard to his abilities as an author, bin Laden was unusually modest: he let someone else write the words. “I am not, as most of our brothers know, a warrior of the word,” he said.

A destroyer, even the brave might fear, She inspires horror in the harbor and the open sea, She goes into the waves flanked by arrogance, haughtiness and fake might,

To her doom she progresses slowly, clothed in a huge illusion,

Awaiting her is a dinghy, bobbing in the waves.

“The Looming Tower” is full of such surprising detail. Al Qaeda’s leaders had all but shelved the 9/11 plot when they realized they lacked foot soldiers who could pass convincingly as westernized Muslims in the United States. At just the right moment Atta appeared in Afghanistan, along with Ramzi bin al-Shibh, Ziad al-Jarrah and Marwan al-Shehhi, all Western-educated transplants, offering themselves up for slaughter. The game was on.

Just as dramatic as the portraits of bin Laden and Zawahiri is Wright’s account of the roots of Islamic militancy — the intellectual, spiritual and material world from which the plotters came. Wright draws a fascinating picture of Sayyid Qutb, the font of modern Islamic fundamentalism, a frail, middle-aged writer who found himself, as a visitor to the United States and a student at Colorado State College of Education in Greeley in the 1940’s, overwhelmed by the unbridled splendor and godlessness of modern America. And by the sex: like so many others who followed him, Qutb seemed simultaneously drawn to and repelled by American women, so free and unselfconscious in their sexuality. The result is a kind of delirium:

“A girl looks at you, appearing as if she were an enchanting nymph or an escaped mermaid,” Qutb wrote, “but as she approaches, you sense only the screaming instinct inside her, and you can smell her burning body, not the scent of perfume, but flesh, only flesh. Tasty flesh, truly, but flesh nonetheless.”

It wasn’t much later that Qutb began writing elaborate rationalizations for killing non-Muslims and waging war against the West. Years later, Atta expressed a similar mix of obsession and disgust for women. Indeed, anyone who has spent time in the Middle East will recognize such tortured emotions.

WRIGHT shows, correctly, that at the root of Islamic militancy — its anger, its antimodernity, its justifications for murder — lies a feeling of intense humiliation. Islam plays a role in this, with its straitjacketed and all-encompassing worldview. But whether the militant hails from a middle-class family or an impoverished one, is intensely religious or a “theological amateur,” as Wright calls bin Laden and his cohort, he springs almost invariably from an ossified society with an autocratic government that is unable to provide any reason to believe in the future. Islam offers dignity, even in — especially in — death. Living in the West, Atta and the others felt these things more acutely, not less. As Wright notes:

“Their motivations varied, but they had in common a belief that Islam — pure and primitive, unmitigated by modernity and uncompromised by politics — would cure the wounds that socialism or Arab nationalism had failed to heal. They were angry but powerless in their own countries. They did not see themselves as terrorists but as revolutionaries who, like all such men throughout history, had been pushed into action by the simple human need for justice. Some had experienced brutal repression; some were simply drawn to bloody chaos. From the beginning of Al Qaeda, there were reformers and there were nihilists. The dynamic between them was irreconcilable and self-destructive, but events were moving so quickly that it was almost impossible to tell the philosophers from the sociopaths. They were glued together by the charismatic personality of Osama bin Laden, which contained both strands, idealism and nihilism, in a potent mix.”

In John O’Neill, bin Laden almost met his match. The supervisor of the F.B.I.’s New York office and of the team assigned to track Al Qaeda in the United States, O’Neill felt, as strongly as anyone in the government, that Al Qaeda was coming to America. He was a relentless investigator, a volcanic personality and sometimes his own worst enemy. In the end he broke himself on a government bureaucracy that could not — and would not — move as quickly as he did. O’Neill and others like him were in a race with Al Qaeda, and although we know how the race ended, it’s astonishing — and heartbreaking — to learn how close it was.

Some of the F.B.I.’s field agents, as we now know, had premonitions of what was coming. When the supervisor of the Minneapolis field office was admonished, in August 2001, for expressing fears that an Islamic radical attending flight school might be planning a suicide attack, he shot back defiantly that he was “trying to keep someone from taking a plane and crashing into the World Trade Center.” Amazing.

The most gut-wrenching scenes are the ones that show F.B.I. agents trying, as 9/11 approached, to pry information from their rivals inside the United States government. The C.I.A., Wright says, knew that high-level Qaeda operatives had held a meeting in Malaysia in January 2000, and, later, that two of them had entered the United States. Both men turned out to be part of the team that hijacked the planes on Sept. 11. The C.I.A. failed to inform agencies like the F.B.I. — which might have been able to locate the men and break up the plot — until late in the summer of 2001.

The fateful struggle between the C.I.A. and F.B.I. in the months leading up to the attacks has been outlined before, but never in such detail. At meetings, C.I.A. analysts dangled photos of two of the eventual hijackers in front of F.B.I. agents, but wouldn’t tell them who they were. The F.B.I. agents could sense that the C.I.A. possessed crucial pieces of evidence about Islamic radicals they were investigating, but couldn’t tell what they were. The tension came to a head at a meeting in New York on June 11, exactly three months before the catastrophe, which ended with F.B.I. and C.I.A. agents shouting at each other across the room.

In one of the most remarkable scenes in the book, Ali Soufan, an F.B.I. agent assigned to Al Qaeda, was taken aside on Sept. 12 and finally shown the names and photos of the men the C.I.A. had known for more than a year and a half were in America. The planes had already struck. Soufan ran to the bathroom and retched.

GREAT stuff. I just wish Wright had given us something, even a chapter, on the hijackings themselves; as it is, he takes us right up to the moment, and then straight to the burning towers. Perhaps he felt that ground was too well-trodden. My other complaint is more substantive. Through the enormous amount of legwork he has done, tracking down people who worked with bin Laden and Zawahiri over the years, Wright has drawn up verbatim reconstructions of entire conversations, some of which took place more than a decade ago. Many of these conversations are riveting. Still, in some cases, it’s hard to believe that memories are that good.

“The Looming Tower” ends near the Pakistani border, where Zawahiri, or someone who looked like him, rode through a village on horseback and then disappeared into the mountains. It’s not a definitive ending; there is no closure. And that’s the point. For as amazing as the story of Al Qaeda and the road to 9/11 is, it’s not over yet. « Previous Page12 Dexter Filkins is a Baghdad correspondent for The Times.

Copyright 2006 The New York Times Company. Reprinted from The New York Times, Book Review, of Sunday, August 6, 2006.