Charles Mackay's Memoirs of the Incredible Popular Superstitions and Madness of Mobs is a classic work that explores the phenomena of mass hysteria, fanaticism, and general silliness that affect human psychology in large groups. The author explores a variety of stories and examples that explain why people are prone to collective insanity from time to time. This book leaves the reader impressed by the depth of his analysis and shows how important it is to remain sane in a society where ideas can spread quickly and cause chaos.