The book "Treatise on the Incubus, or Nightmare, Disturbed Sleep, Terrible Dreams and Night Visions" by the author John Augustine Waller is a study devoted to the phenomena that accompany a person while observing his own sleep. The author examines such phenomena as the incubus, or nightmare, the conversation of a reflected dream, terrible dreams and night visions. Waller examines the psychological and physiological aspects of these phenomena in detail, based on modern scientific data and personal experience. This book helps us better understand the nature of our nightmares and helps us find ways to manage them.