Check out Ali Soufan's book (http://www.amazon.com/The-Black-Banners-Against-al-Qaeda/dp/...). I'll loan you my copy if you're in the Boston area. He has had quite an interesting career. According to the book and the New Yorker, it turns out that Soufan probably would have stopped 9/11 had the proper information been shared with him. Again according to his book, he was also a major voice against the use of enhanced interrogation techniques and had the chops to back it up. The book states that he was one of the most effective interrogators of captured Al Qaeda suspects and his method essentially boiled down to serving them tea and debating the Quran with them in Arabic.

For a general idea of what the book goes into, you can see Soufan's profile in the New Yorker: http://www.newyorker.com/archive/2006/07/10/060710fa_fact_wr.... In the (Pulitzer Prize-winning) reporter's own words: "Soufan became America’s best chance to stop the attacks of September 11th.".