This is a classic title, Extraordinary Popular Delusions and the Madness of Crowds.
The crowd isn't always right. In fact, quite often, it falls prey to delusion, lack of perspective, group think and wishful thinking.
Bottom line: you gotta understand the psychology of ignorance and emotion.
First published in 1841, it analyses three great outbreaks of mass-investment psychosis: the Mississippi Scheme and the South Sea Bubble in the 18th century, and Dutch tulipmania in the 17th century, which is also the subject of Joseph de la Vega's eyewitness account, first published in 1688. All three instances provided anecdotes as scary as any stemming from the 1929 crash.
Read the full book review (excerpt above) here.