I've been going through this. I'm currently on History of the C.P.S.U. (B). There are a shit ton of books on the list and it has them organized into levels going from beginner, intermediate, advanced, and very advanced. Each level has 3 or 4 trimesters, each with a generous selection of works to read. It also has a background reading section for pre-beginners. While the background reading list has some of the usual suspects like the 'Festo, Socialism: Utopian and Scientific, and Stalin's introductory text Dialectical and Historical Materialism, it also has some lesser seen picks like works that Adoratsky and Cornforth made on dialectical materialism.
Speaking of lesser seen picks, there are some works on several of the levels I don't normally see mentioned here or on Hexbear, like the Shanghai textbook on political economy, Documents of the Great Proletarian Cultural Revolution, some Plekhanov, some Lukacs, some of Gramsci's works that aren't his prison notebooks, etc.