From The Telegraph:
Before the 2003 invasion of Iraq, I doubt many people in Britain knew the difference between a Sunni and a Shia. But since the civil war began in 2003, there has been considerable curiosity about the complexity of religious and political divisions in the Arab world.
In Eclipse of the Sunnis, the American journalist Deborah Amos describes how nearly two million mainly Sunni Iraqis have fled their country since the Americans and British invaded seven years ago. Her title references a now famous theory proposed by King Abdullah of Jordan that since the war a “Shia crescent” of influence has developed from a newly emboldened Iran through Shia-ruled Iraq, Syria and Hizbollah in Lebanon. Abdullah contrasted these radical forces with the settled (some might say pliant and undemocratic) Sunni states such as Jordan, Saudi Arabia and Egypt. The message was designed as a rebuke to the US for unleashing a Shia revival that would work against its interests.
More here.