Book excerpt: Extreme Killing: Understanding Serial and Mass Murder provides a comprehensive, fascinating overview of multiple homicide, including both serial and mass murder. Adopting a unified conceptual framework for understanding these divergent forms of extreme killing, this book illustrates the many violent expressions of power, revenge, terror, greed, and loyalty using contemporary and classic case studies in multiple murder. In Extreme Killing, renowned experts James Alan Fox and Jack Levin examine the theories of criminal behavior and apply them to a multitude of well-known and lesser-known cases from around the world. The authors draw upon research from two large data sets - one comprised of serial killers and the other of those who have committed massacres. The book presents the many commonalities among multiple murders and also focuses on the varieties of serial and mass killing. The authors address the characteristics of both killers and their victims, and, in their concluding chapter, discuss the special concerns of multiple murder victims and their survivors.