If there is even a one percent chance that America will be attacked by any organization in the world, America considers it as credible threat and acts now. Whether the threat is real or not is not important. This is the Cheney Doctrine that governs American Policy for Foreign Affairs and terrorism in future.
The book starts on the day of September 11 attacks and sketches American response to the event. Interesting insights and anecdotes into the dealings of power centers at Capitol hill, various intelligence agencies and foreign governments make the book really interesting. Read the book if you like reading current history.