Darryl Jones manages to pack in a lot of information into a short volume in Sleeping with the Lights On: The Unsettling Story of Horror. In his introduction, Jones describes the long tradition of depicting horrific scenes in the works of lore and literature from the earliest civilizations. He discusses the “catharsis” theory that posits that images of violence can vicariously fulfill people’s natural inclinations without requiring overt action. In contrast, current psychologists have hypothesized the idea that experiencing simulated violence can lead to an increase in equivalent behavior and acceptance. Jones uses the book to elaborate on his own idea that tales of horror are a way of testing limits and a reflection of the level of tolerance within a society. He clarifies the vocabulary of the genre and its subcategories, using examples from books, film, and podcasts. Jones demonstrates how humans may have common innate sources of anxiety and fear that span cultural differences, but that the form that these take varies over time and development. While some of our well-known external “monsters” have become iconic and have endured over time, other new ones have emerged due to advances in technology. Our increased knowledge about mental processes and illnesses has altered our understanding of non-normative behavior, leading to changes in how aberrant examples are perceived. Sleeping with the Lights On is concise and interesting, providing a nice overview to the history of horror and our underlying fascination with it. Jones also includes an appendix with additional resources for readers interested in more in-depth exploration. This is a great basic “primer” for a genre that is increasingly becoming accepted as a true art form.