This sober and detailed analysis of Islamist terrorism in Europe generalizes not just from the attacks that have succeeded but also from the over two-thirds of planned attacks that have been foiled. Nesser shows that although their basic goals are constant, Islamist terrorists adapt their tactics with the times. In recent years, heightened security has made complex bombings and aircraft hijackings all but impossible—so terrorists have gone minimalist. Attacks today tend to be one-man operations, carried out with vans and knives. Most perpetrators are refugees or European-born jihadists. They are almost always motivated by religion, and they communicate with outside groups through encrypted messaging tools, such as WhatsApp. This form of terrorism is, as Nesser says, “less lethal, but almost impossible to stop.” So although the annual European death toll from terrorism is far below what it was during the 1970s and 1980s, the number of attacks is higher than ever. Nesser concludes that military operations abroad do less to quash terrorism than sound policing at home. Police, he says, should focus on stopping “entrepreneurs”—skilled jihadist activists who assist perpetrators—through aggressive surveillance. He ends on a pessimistic note, but perhaps the striking decline in successful European terrorist attacks over the past year would lead him to reconsider his conclusion.