(recommend watching this entire series tbh. Bonus: the guy himself was a leftist, very familiar with Marx, got denied tenure at the college because of union organising work)
There are two kind of views on this>Postmodernism is an ideological system with a bunch of specific statements or content like the >>1339 rejection of metanarratives, breaking the fourth wall, the death of the author, the deconstruction and disruption of established forms, etc. etc.
<This is fucking dogshit, who gives a fuck, it's just a bag of beliefs and views and ways to analyse literature in the 1980s English department and 1990s Architecture grant market>Postmodernism is an attempt to understand these new developments in culture, from a Marxist and critical theory viewpoint, and trying to work out from culture what was happening in the base, in the same way as one analyses an animal's shit (culture) to determine a sickness in its gut (economic structure). This is especially important because the postmodern really got going hardcore post-1991, i.e. post USSR, post "death of communism". between 1968 and 1991 (or say 1998) we saw capitalist culture transition into a new awful condition, and our job is to understand it.
<This is based and good and I recommend it highly
Read:>Guy Debord (Society of the Spectacle; and, Comments on the Society of the Spectacle)>Frederic Jameson (Postmodernism, Or, The Cultural Logic of Late Capitalism; a bunch of other shit)>early-mid career Slavoj Zizek (The Sublime Object of Ideology; works generally up to, say, Welcome to the Desert of the Real)>Baudrillard (System of Objects and Simulacra and Simulacrum)