One of the least remarked upon aspects of the war in Iraq, at least in the American press, has been how conflict and instability in that country have shaken the delicate balance of power between Sunni and Shia throughout the wider region. Nasr, professor of Middle East and South Asia politics at the Naval Postgraduate School, tackles this question head-on for a Western audience. His account begins with a cogent, engrossing introduction to the history and theology of Shia Islam, encapsulating the intellectual and political trends that have shaped the faith and its relations with the dominant Sunni strain. Nasr argues that the Shia Crescentâ€”stretching from Lebanon and Syria through the Gulf to Iraq and Iran, finally terminating in Pakistan and Indiaâ€”is gathering strength in the aftermath of Saddam's fall, cementing linkages that transcend political and linguistic borders and could lead to a new map of the Middle East. While Nasr's enthusiasm for Iraq's Shiite leader Ayatollah Sistani sometimes borders on the hagiographic, and he makes a number of uncharacteristic errors, such as conflating the Syrian Alawi community with the Turkish Alevis, his book is worthwhile reading for those seeking a primer on the second-largest Muslim sect.