Husain offers a layman’s, not a theologian’s, understanding of Islam. As a young man, he immersed himself in Salafism, the literalistic and puritanical interpretation of Islam spread by Saudi Arabian proselytizers and funded by the country’s petrodollars. Later, he rediscovered Sufism, a faith and culture that he estimates has been adopted by around 80 percent of Muslims over the religion’s 1,400-year history. Sufism embraces music, dance, poetry, and sex as aspects of the quest for God. It respects other faiths and accepts human frailty. Husain believes the Salafists and other orthodox extremists have hijacked Islam. He has founded a think tank, Quilliam, to help more moderate Muslims win it back. It is not clear whether Husain’s engaging treatise is aimed at Muslims or non-Muslims, but he evidently thinks that Muslims are primarily responsible for the emergence of extremism in their communities. There is an urgent question underlying the book: Is Salafism an aberration from a religion characterized by tolerance, reason, and agency for women, or is it the tip of an iceberg of literalism, sexism, and violence? Husain clearly believes the former, although he does not address the question in detail.