Lawrence Wright has an article in the New Yorker about the Madrid bombings. In short, the bombings were a dramatic departure from al-Qaeda ideologically - focusing on near term political disruption, rather than a clash of civilizations - but were carried out by a closely affiliated group. Aside from the new info. on Madrid, it largely retreads the 03/04 IISS Strategic Survey. IISS, which I would generally categorize as center-right, has done some of the best theorizing on al-Qaeda, including analyzing its decentralization into networks following the invasion of Afghanistan, which counter-intuitively may have strengthened it.