You might think that militant Islamists would have a firm grip on at least one thing: Islam. Think again. (This story is based on a radio interview. Listen to the full interview.) In 2013, 22-year-old Britons Yusuf Sarwar and Mohammed Ahmed were preparing to leave the UK and join extremist groups in Syria. But first, they bought some reading material from Amazon. One of those books was "The Koran for Dummies." “Even though they may have ordered it, I don't think they read it,” says Sohaib Nazeer Sultan, who's the author of the book and Princeton University's first campus imam....