Modern people know about obsessive states firsthand. How often can we simply not stop—frantically checking messages on our smartphone, trying to pass a level in a video game, or buying things even when there’s nowhere to put them. But where is the line between normality and pathology—and, most importantly, when are purposefulness and obsession a path to creativity and success, and when do they become a barren and dangerous waste of effort and time? In the book, the author tells the history of how this question has been studied, what obsessive behavior is different from addiction, and how the “compulsive brain” works. The relevance of the problem, conversations with leading specialists in obsessive behavior, and the fates of real patients make this book equally informative and engaging.