[A]s Jane Mayer, a staff writer for The New Yorker, makes clear in “The Dark Side,” a powerful, brilliantly researched and deeply unsettling book, what almost immediately came to be called the “war on terror” led quickly and inexorably to some of the most harrowing tactics ever contemplated by the United States government. The war in Iraq is the most obvious and familiar result of the heedless “toughness” of the new administration. But Mayer recounts a different, if at least equally chilling, story: the emergence of the widespread use of torture as a central tool in the battle against terrorism; and the fierce, stubborn defense of torture against powerful opposition from within the administration and beyond. It is the story of how a small group of determined men and women thwarted international and American law; fought off powerful challenges from colleagues within the Justice Department, the State Department, the National Security Council and the C.I.A.; ignored or circumvented Supreme Court rulings and Congressional resolutions; and blithely dismissed a growing clamor of outrage and contempt from much of the world — all in the service of preserving their ability to use extreme forms of torture in the search for usable intelligence. New York Times