Here's a comic example of Marxist literary theory in action:Marxist literary theories tend to focus on the representation of class conflict as well as the reinforcement of class distinctions through the medium of literature. Marxist theorists use traditional techniques of literary analysis but subordinate aesthetic concerns to the final social and political meanings of literature. Marxist theorists often champion authors sympathetic to the working classes and authors whose work challenge economic equalities found in capitalist societies. In keeping with the totalizing spirit of Marxism, literary theories arising from the Marxist paradigm have not only sought new ways of understanding the relationship between economic production and literature, but all cultural production as well. Marxist analyses of society and history have had a profound effect on literary theory and practical criticism. (Internet Encyclopedia of Philosophy)
Speaking of comics and sf lit:
According to Terry Eagleton (the latest, greatest Marxist literary critic): "Marxist criticism is not merely a 'sociology of literature', concerned with how novels get published and whether they mention the working class. Its aim is to explain the literary work more fully; and this means a sensitive attention to its forms, styles and meanings. But it also means grasping those forms, styles and meanings as the product of a particular history."
So how would you use Marxist literary theory to critique a text? How is the book itself a product of history? What social and material conditions existed at the time of its creation? Why was it necessary? Eeekk, it's like Robert Heinlein's "All You Zombies--" with creations swallowing creations, birthing creations . . . but I digress.
So as you read novels or watch movies, think about how the story reflects different socio-economic classes. For works of science fiction and fantasy: How do economies on different planets, alternative histories, or realities work? Who gets left out? How are economic systems organized? What is wealth? What is currency? What is progress? How are workers portrayed? Is there economic equality/inequality? What makes a dystopia or a utopia and how is that related to economic wealth and/or equality? You can ask these seem kinds of questions about any text, visual or written.