Jason Burke is one of the world's leading experts on militant Islam. He embedded with the Kurdish peshmerga (currently at war with ISIS) while still in college. He was hanging out with the Taliban in the late 1990s. He witnessed the bombing of Tora Bora in Afghanistan in 2001 firsthand. With the current emergence of ISIS in Iraq and Syria and the resurgence of the Taliban in Afghanistan and Pakistan, no one is as well placed as Burke--whose previous...