No god but God: the Origins, Evolution, and Future of Islam by Reza Aslan, Random House, New York 2006.
This is a highly readable account of the evolution of Islam by an internationally acclaimed religion scholar with a gift for writing complex history in an uncluttered way. He argues that terrorism by Muslim extremists is not about Muslims and Christians or Islam and the West, but rather the internal struggle/reformation within Islam to decide the shape of Islam's future. The attacks on the West inviting subsequent retaliation are ploys to coerce Muslims to bond together against a common enemy, since Islamic unity is a high priority for all Muslims.