"The Proletarian in Spain and the Negro in Cuba" is a careful analysis of social and political processes by its author, Ramon Espinosa. The book examines the issue of social labor in Spain and the phenomenon of the liberation of the African people in Cuba. The main themes of the book are class struggles in Spanish society and the slave system on the island of freedom. Espinosa draws attention to the importance of uniting the proletariat and money against slavery in the struggle for social rights and freedom. With the help of extensive analysis and specific historical examples, the author creates an interesting and informative narrative that helps to understand the complex aspects of social relations in Spain and Cuba in the 19th century.