During early 1919, overwhelmed by turmoil about the end of his career, devastation at the recent war, and deep mental distress fostered throughout his life, the virtuoso ballet dancer Vaslav Nijinsky became consumed by psychosis. He documented this experience in his remarkable diary, written over a frantic six weeks. Nijinsky’s private exploration of his dreams, anguish, and paranoia is an enlightening read, the more so because his subsequent story tells us much about the development of psychiatric treatment.

For a man who found global fame with the Ballet Russes during the early 20th century, …