A more deadly consequence of this heedlessness was the American invasion of Iraq in 2003 on the false belief that Saddam Hussein possessed an arsenal of chemical and biological weapons. An exchange from that time conveys the mind-set of the Bush administration. When Stephen Hadley, the deputy national security adviser, told Paul Wolfowitz, then the deputy defense secretary, that there was no intelligence linking Al Qaeda to Saddam Hussein, “Wolfowitz tightened his lips,” Eichenwald writes. “ ‘We’ll find it,’ he said with certainty in his voice. ‘It’s got to be there.’ ” The run-up to the Iraq war also elicits one of the most pungent lines in the book. After Bush told Jacques Chirac that biblical prophecies were being fulfilled and specifically that “Gog and Magog are at work in the Middle East,” the French president decided, in Eichenwald’s words, that “France was not going to fight a war based on an American president’s interpretation of the Bible.”

The sheer incompetence of the interrogators of supposed terrorists comes as a genuine surprise. The C.I.A. seemed to know little about how to actually question people, and began taking advice from an uninformed, inexperienced psychologist whom Eichenwald labels “a fool.” At Guantánamo, the advice of law enforcement specialists was put aside, and interrogations slipped from unprofessional to brutal to illegal. “Rather than acknowledging defeat, the intelligence officers wanted to double down on a failed approach,” Eichenwald writes. “Harsh interrogations would work, they were arguing, if only they were harsher.” F.B.I. agents on the scene, witnessing this descent, discussed whether they would be obliged to arrest the interrogators rather than let them continue down this savage path.

Eichenwald’s prose occasionally lapses into the style of Tom Clancy’s novels, complete with the bureaucrat-as-hero theme and overwrought prose: “The electronic timer on a concealed briefcase bomb flashed red, its digits counting down from five minutes. A small fan quietly whirred, generating a breath of air that could disperse enough sarin gas to kill everyone within several yards.” The histrionic tone seems unnecessary when writing about some of the most dramatic events of our time. And it is especially grating when the Clancyesque details are wrong, as when he portrays Donald Rumsfeld, then defense secretary, as sharply decisive when he was notorious inside the Pentagon for being imperious but vacillating.

There are also some odd errors. The people of Afghanistan are “Afghans,” not “Afghanis,” which is the currency. Yet Eichenwald refers to them this way more than 20 times. Likewise, Aq Kupruk is near the Afghan town of Mazar-i-Sharif, but is a village, not a city, as Eichenwald writes. And Gen. Wesley Clark was retired from military service when he is shown on a visit to the Pentagon, so why is he depicted as having “dozens of medals and service ribbons gleaming on his chest”? There is still room for a truly comprehensive history of the great panic that overtook the Bush administration, much of the American media and some of the American people in the months and years after 9/11. But in this book, Kurt Eichenwald has recorded a key portion of that story. He brings home the fundamental rashness and recklessness of the American response to the Sept. 11 attack. Had our leaders abided by our Constitution, not only would they have better supported our values, they would have been more effective in responding to terrorism. That is the sad lesson of this book.