Ed Husain is a former Islamic extremist who has since rejected radicalism, and now advises governments on managing anti-extremist programmes. He knows Islam intimately, and this book is an essential read in these times of extremism, and the rise of ISIS, Al Qaeda, the Taliban etc. He explains the origin of Islam, the structure of sharia, and defines and explains the confusing different strains of Islam - Sufism, Salafism, Wahhabism, the Sunni-Shi'a schism etc. It's an elegant overview of the Islamic world, and deserves to be widely read.