"The Crowd" is a masterpiece of psychology that thoroughly discusses politics, economics, and management, and is known as the pioneering work of group psychology. The whole book analyzes the various characteristics and causes of groups in a simple and easy-to-understand way, and describes the collective mentality exquisitely. It has exerted a huge influence on people's understanding of the role of collective behavior and thinking on social psychology. In the book, the author uses the insight of a prophet to successfully describe almost all major events in the next hundred years or so, including two world wars and numerous democratic revolutions.