TLDR: There are different writing styles. Don’t start with dense essays, try to start with reading more prepared for the average worker. Reading speed and comprehension requires practice. You don’t teach baby using long novels, start easy and slowly increase your objectives.

Long: Honestly, it depends on the author. In some cases, the reading is made very accesible (more of a narrative approach than an essayist one) and reading faster helps. Usually the ones aimed at the average proletariat.

In other cases, the message needs some analysis and speed isn’t as important as comprehension and analysis of words, because that will be the time bottleneck. Those are often essays prepared for academic and political study.

Marx is kind of the classical example of very extensive essays that you start but can’t finish without using a commented version with predigested footnote comments. Unfortunately, he never got to finish his books, let alone produce easier reading versions.

From my experience, Lenin, Parenti and the communist manifesto (actually only describing socialist complaints) are quite accesible. They also allow for deeper/slower analysis on later reads.