No wonder the former Rumsfeld capo, Douglas Feith, is trying to discredit a damaging interview he gave to the British lawyer Philippe Sands for another recent and essential book on what happened, “Torture Team.” After Mr. Sands previewed his findings in the May issue of Vanity Fair, Mr. Feith protested he had been misquoted  apparently forgetting that Mr. Sands had taped the interview. Mr. Feith and Mr. Sands are scheduled to square off in a House hearing this Tuesday.

So hot is the speculation that war-crimes trials will eventually follow in foreign or international courts that Lawrence Wilkerson, Colin Powell’s former chief of staff, has publicly advised Mr. Feith, Mr. Addington and Alberto Gonzales, among others, to “never travel outside the U.S., except perhaps to Saudi Arabia and Israel.” But while we wait for the wheels of justice to grind slowly, there are immediate fears to tend. Ms. Mayer’s book helps cement the case that America’s use of torture has betrayed not just American values but our national security, right to the present day.

In her telling, a major incentive for Mr. Cheney’s descent into the dark side was to cover up for the Bush White House’s failure to heed the Qaeda threat in 2001. Jack Cloonan, a special agent for the F.B.I.’s Osama bin Laden unit until 2002, told Ms. Mayer that Sept. 11 was “all preventable.” By March 2000, according to the C.I.A.’s inspector general, “50 or 60 individuals” in the agency knew that two Al Qaeda suspects  soon to be hijackers  were in America. But there was no urgency at the top. Thomas Pickard, the acting F.B.I. director in the summer of 2001, told Ms. Mayer that when he expressed his fears about the Qaeda threat to Mr. Ashcroft, the attorney general snapped, “I don’t want to hear about that anymore!”

After 9/11, our government emphasized “interrogation over due process,” Ms. Mayer writes, “to pre-empt future attacks before they materialized.” But in reality torture may well be enabling future attacks. This is not just because Abu Ghraib snapshots have been used as recruitment tools by jihadists. No less destructive are the false confessions inevitably elicited from tortured detainees. The avalanche of misinformation since 9/11 has compromised prosecutions, allowed other culprits to escape and sent the American military on wild-goose chases. The coerced “confession” to the murder of the Wall Street Journal reporter Daniel Pearl by Khalid Sheikh Mohammed, to take one horrific example, may have been invented to protect the real murderer.

The biggest torture-fueled wild-goose chase, of course, is the war in Iraq. Exhibit A, revisited in “The Dark Side,” is Ibn al-Shaykh al-Libi, an accused Qaeda commander whose torture was outsourced by the C.I.A. to Egypt. His fabricated tales of Saddam’s biological and chemical W.M.D.  and of nonexistent links between Iraq and Al Qaeda  were cited by President Bush in his fateful Oct. 7, 2002, Cincinnati speech ginning up the war and by Mr. Powell in his subsequent United Nations presentation on Iraqi weaponry. Two F.B.I. officials told Ms. Mayer that Mr. al-Libi later explained his lies by saying: “They were killing me. I had to tell them something.”

That “something” was crucial in sending us into the quagmire that, five years later, has empowered Iran and compromised our ability to counter the very terrorists that torture was supposed to thwart. As The Times reported two weeks ago, Iraq has monopolized our military and intelligence resources to the point where we don’t have enough predator drones or expert C.I.A. field agents to survey the tribal areas where terrorists are amassing in Pakistan. Meanwhile, the threat to America from Al Qaeda is “comparable to what it faced on Sept. 11, 2001,” said Seth Jones, a RAND Corporation terrorism expert and Pentagon consultant. The difference between now and then is simply that the base of operations has moved, “roughly the difference from New York to Philadelphia.”