Most colorful anarchist explains philosophy of history, oppression by organized religion, etc. Mind-opening.
Here's a sample of other books in this Dover category
The ABC of Anarchism by Alexander Berkman, Paul Avrich, Emma Goldman This book by one of the most gifted writers for the anarchist movement answers some of the charges made against it and presents the case for communist anarchism clearly and intelligently.
Anarchism: A Collection of Revolutionary Writings by Peter Kropotkin Includes "Law and Authority," arguing social control through custom and education, and "Prisons and Their Moral Influence on Prisoners," expressing the evils of the prison system, and other documents.
The Revolution Betrayed by Leon Trotsky, Max Eastman One of Marxism's most important texts, this 1936 polemic explores the fate of the Russian Revolution after Lenin's death. A brilliant and profound evaluation of Stalinism, it prophesies the inevitable collapse of the Soviet Union.