The book "Crowd Behavior: A Psychological Study" was written by the famous American psychologist Everett Dean Martin. In this book, the author examines the phenomenon of crowd behavior in detail, having analyzed the psychological aspects governing human masses. Martin explores the effects of collective behavior at the individual level and explores theories that explain why people in a crowd can change their behavior and make decisions that they would not make individually. Martin's work is a valuable addition to the understanding of crowd psychology and reveals deep aspects of collective human behavior.