The Crowd: A Study of the Popular Mind
by Gustav Le Bon.
The book had a profound impact not only on Freud but also on such twentieth-century masters of crowd control as Hitler and Mussolini – both of whom may have used its observations as a guide to stirring up popular passions. In the author’s words, “The masses have never thirsted after the truth. Whoever can supply them with illusions is easily their master; whoever attempts to destroy their illusions is always their victim.” Although the volume focuses on crowd psychology, it is also brilliantly instructive on the effects of the generally accepted beliefs of a nation’s citizenry on the processes of history.
https://archive.org/details/in.ernet.dli.2015.223078/mode/2up
https://en.wikipedia.org/wiki/The_Crowd:_A_Study_of_the_Popular_Mind