Book excerpt: The Dark Side is a dramatic, riveting, and definitive narrative account of how the United States made self-destructive decisions in the pursuit of terrorists around the world—decisions that not only violated the Constitution, but also hampered the pursuit of Al Qaeda. In spellbinding detail, Jane Mayer relates the impact of these decisions by which key players, namely Vice President Dick Cheney and his powerful, secretive adviser David Addington, exploited September 11 to further a long held agenda to enhance presidential powers to a degree never known in U.S. history, and obliterate Constitutional protections that define the very essence of the American experiment. With a new afterward. One of The New York Times 10 Best Books of the Year National Bestseller National Book Critics Circle Award Finalist A Best Book of the Year: Salon, Slate, The Economist, The Washington Post, Cleveland Plain-Dealer