What is a nightmare? Why have nightmares filled novels, films, and computer games, and why has the experience of a nightmare become a mass need in modern culture? Psychology, cultural studies, and literary studies do not provide answers to these questions, since the nightmare has never been considered by scientists as a subject worthy of serious attention. However, for the authors of the “novel of mental states,” the nightmare was the meaning of creativity. N. Gogol and C. Metyurin, F. Dostoevsky and T. Mann, H. Lovecraft and V. Pelevin staged bold experiments on their heroes and readers in order to capture the nightmare in their works. Dina Khapaeva's book for the first time attempts to read these texts as studies on the nature of nightmare and to restore the mosaic of coincidences thanks to which a literary experiment turned into our everyday life.