I’ve have already given this advice IRL before, and considering no one has commented anything similar, I think it applies here as well:

If you’re looking for a introduction to communism and Marxism, you should read the manifesto, it’s cut and dry, short and direct to the point it’s trying to pass, it’s literally made to be understandable by everyone.

But if you want more than that and are looking to actually understand and study Marxism, which I believe is the point of a book club, then you should definitely start reading about the Marxist world outlook, dialetical materialism, most of the mistakes and misunderstandings of leftist both here and IRL come from skipping this crucial step.

So if you are having trouble with the main texts, if you can understand diamat every book of Marx, Engels, Lenin, etc., you read afterward will much easier to comprehend. On that note, to me, the best 3 texts about their philosophy are: Mao’s “On Contradiction”; Engels’ “Socialism Utopian and Scientific”; and M. Cornforth’s “Materialism and the Dialetical Method”, which I’d recommend then to be read in this order, and if after that you still want more, Cornforth’s last book ends with further recommendations.

So basically, if you are having trouble understanding Marxism you should start from the very beginning and understand their method before jumping straight to the more famous and much more dense books.