This is a list of some basic texts covering all things leftism, philosophy, etc.
The Principles of Communism - Friedrich Engels Ranking: 8/10
This text is an extremely short read that is formatted like a FAQ for communism. It is composed of 25 questions that range from education to religion to the character of the proletarian and bourgeois classes.
Wage Labour and Capital - Karl Marx Ranking: 10/10
Value Price and Profit - Karl Marx Ranking: 8/10
The German Ideology - Karl Marx & Friedrich Engels Ranking: 9/10
The Manifesto of the Communist Party (The Communist Manifesto) - Karl Marx & Friedrich Engels Ranking: 6/10