McDermott has written what is so far the definitive narrative of the 9/11 hijackers. He divides his book into three parts: First, he profiles the backgrounds and personality profiles of the hijackers, many who started as regular citizens and slowly drifted into their extremism, often by chance. Second, he explains the political forces in Soviet-occupied Afghanistan that helped to revive Jihad and give power to Osama Bin Laden. Third, he focuses on the actual plot to hijack the planes on 9/11. The reportage is remarkable and provides clues to the hijackers' personalities that have so far not been publicized. What's scary is the effective way the author shows the hijackers often came from privileged backgrounds and then drifted into the fringes of society where, needing direction and identity, they were susceptible to the extremist rhetoric of fundamentalism and violent jihad. Where I might disagree with McDermott is his characterization of the hijackers as "fairly ordinary men." Perhaps I have a different definition of "ordinary" than does McDermott who uses hundreds of salient illustrations to paint these men anything than as ordinary: They are often portrayed as sullen spoiled narcissistic brats and bullies. One of the most prominent of the hijackers, Mohamed Atta, in particular is an extreme personality study in repressed sexuality, narcissism, and sociopathic hatred of others. He cannot smile or enjoy life in the slighest so that when he eats food he mutters to himself how boring and tedious the task of eating is. Everyone who knew him, even people who shared in his beliefs, found him an obnoxious presence. Sullen, brooding, and controlling, he made the hairs on people's neck bristle whenever he entered a room. In spite of his fastidious religious adherence, he takes to the mysterious and disturbing desire to wear eye mascara. I'll let you decided if he is "ordinary" or not. In any event, Atta, like the others, is misogynistic; women are shunned and held in contempt. The total sum picture you get of these hijackers is a bunch of malignant malcontents who need an extreme cause to be a vehicle for their personal frustration and deeply-set anti-social tendencies.
For an excellent companion book to better understand the types of personalities who get drawn to extreme forms of belief, I highly recommend Eric Hoffer's slim masterpiece The True Believer.