Pulling three chapters from his polemical text, Anti-Duhring, Engels compiles one of the most influential works in popularizing Marxism -- Socialism: Utopian and Scientific. Edited by Karl Marx, this was the text that they both intended to help spread a simpler version of Marxism that did not require dense economic readings.
The first chapter demarcates Marxism as a scientific socialism from its predecessors, the utopian socialists. The second chapter explains dialectics and materialism, two foundational concepts to understand Marxist philosophy. The final chapter is an analysis of capital, noting the anarchy of the market and the progression towards the next stage of society -- communism.
Original text: https://www.marxists.org/archive/marx/works/1880/soc-utop/index.htm
Cover by @loudowicko