More than a century before Alan Greenspan coined the phrase 'irrational exuberance' to describe the speculative bubble inflating technology stocks, Charles Mackay was recording the history of 'tulipomania', a speculative madness surrounding the value of tulips in the 18th century that was the ruin of many Dutch and English investors. This is only one of the 'extraordinary popular delusions' documented by Mackay in a fascinating study of group psychology. He also describes notorious witch hunts, haunted houses, the Crusades, beliefs in fortune tellers and in the magical power of alchemy, veneration of relics, bogus health cures and health scares, and many other examples of human credulity and flights from reason. This work is a true classic in the study of paranormal beliefs, a funny, shocking, and unbelievable yet true history of human gullibility.