Aug. 14 (Bloomberg) -- ``Who are these mass murderers and why do they hate us?''

In the days after 9/11, those were the questions everyone was asking. Answers were scarce, scattered and difficult to comprehend.

Five years later, Lawrence Wright, a staff writer for the New Yorker, has answered many of those questions (along with others that ought to have been asked). ``The Looming Tower: Al- Qaeda and the Road to 9/11'' penetrates the Islamist terrorist network, offering startling insights, odd details and finally, at long last, full portraits of the men behind the attacks.

What comes as a surprise is not their philosophy or their beliefs, although Wright does a masterful job of explaining both. Here, presented coherently and objectively, are the lives of Osama bin Laden, Dr. Ayman al-Zawahiri and their cohorts, in all their human dimensions.

Who knew that bin Laden was given to napping when he and his mujahadeen were pinned down by Soviet mortar fire in Afghanistan in 1987? That he was a lousy businessman, swindled out of $110,000 by a man who later became the FBI's first al-Qaeda informant? That he gave his daughters home schooling in math and science? That two of his wives commuted to university jobs in Saudi Arabia while the family lived in Sudan?

Those details don't explain why bid Laden ordered the murder of thousands of Americans. They do, however, release him from the trap of caricature and stereotype, which so often make him too evil to be true.

Remarkable Research

To get this kind of detail about the world's most wanted men, Wright dug into a trove of documents and correspondence captured or found by U.S. investigators and journalists in Afghanistan, Bosnia and elsewhere. When he couldn't get a visa to Saudi Arabia, Wright found a job mentoring young journalists at a Saudi newspaper, gaining rare first-hand insight into a complex society.

Sources on three continents (whose names fill four pages at the back of the book) not only gave him fresh information. They also allowed him to weed out oft-repeated stories which, when double-checked, often turned out to be untrue. That kind of rigorous reporting makes the book an invaluable guide to the murky world of al-Qaeda and its allies.

Moreover, Wright tells this powerful, important tale extremely well, with a fluid style that takes us from Egypt to Saudi Arabia, Afghanistan to Sudan, tracking the intricate relationship among the various jihadi movements. He traces the intellectual origins of al-Qaeda to an Egyptian named Sayyid Qutb, the grandfather of modern Islamic fundamentalism, who would be hanged (and thus martyred), by General Gamal Abdul Nasser in 1966. An exchange student at what was in the late 1940s the Colorado State College of Education in Greeley, he returned home espousing the anti-Americanism that became a main current in radical Islamist thought.

Against Modernism

``His central concern was modernity,'' writes Wright. ``Modern values -- secularism, rationality, democracy, subjectivity, individualism, mixing of the sexes, tolerance, materialism -- had infected Islam, through the agency of Western colonialism. America stood for all that.''

Bin Laden's war against the U.S. came belatedly, after he and his Afghan allies forced the Soviet army into a retreat -- with U.S. help. He did unleash tirades against the U.S. as early as 1982, after the American-backed Israeli invasion of Lebanon.

``As I looked at those demolished towers in Lebanon, it entered my mind that we should punish the oppressor in kind,'' bin Laden said prophetically, according to Wright. In the late 1990s, bin Laden teamed up with al-Zawahiri (an Egyptian doctor who, like himself, came from a privileged family) to patch together al-Qaeda's rationale for its jihad against the U.S.

Fatwa

``The main point of their diagnosis was that the Islamic nation was in misery because of its leadership,'' writes Wright. ``The jihadis then asked themselves who was responsible for this situation.'' The broad answer was a Christian-Jewish conspiracy. The short answer was the U.S. The result was a fatwa, published by Zawahiri in 1998, declaring that killing Americans and their allies was the individual duty of all Muslims.

Wright tracks another road leading to 9/11, this one in the U.S., where the FBI and the CIA were locked in a rivalry that was to have tragic consequences. This story has now been told many times, as has the tangled life of John O'Neill, the ex-FBI agent whose obsession with al-Qaeda ended on 9/11 when he died in the World Trade Center.

All this is worth covering -- but perhaps, given the depth and scope of Wright's investigation into al-Qaeda, it should have been another book. His argument, no doubt, would be that 9/11 would never have happened had the CIA and FBI together understood the threat and acted in concert rather than at cross purposes.

``The Looming Tower'' is published by Alfred A. Knopf (470 pages, $27.95).

(Celestine Bohlen is a reporter for Bloomberg News. The opinions expressed are her own.)

To contact the reporter on this story: Celestine Bohlen in Paris at cbohlen1@bloomberg.net.

Last Updated: August 14, 2006 00:09 EDT