We say this all the time. It's basically an expression, isn't it? It can be advise, bragging, scorn, mockery. It's all become a bit ephemeral.
That's not to say that people shouldn't read theory. Without revolutionary theory, there can be no revolutionary movement. Even so, isn't it a bit silly to suggest, even implicitly, that being a Marxist or communist boils down to a familiarity with the source material? If that's not book worship, I don't know what is.
I understand that this is, on some level, an accusation. I am suggesting that many of our communities are caught up in a somewhat liberal, idealist mindset. We all have an ideology, a set of opinions about the world which we express and propagate at the expense of our competitors. Can we seriously deny this is what we are doing?
If Marxism-Leninism is a science, there must be some technical aspect. What are we supposed to do in the world? How do we do it? And how do we know if it's working?
i tried reading das kapital multiple times, 1 book by lenin 1 time and always failed in under 10 pages. has this happened to you too? if yes, try stalin! (not claiming he was the best or smartest theorist or whatever, and i dont claim to understand "communist science", but this dude knew how to summarize and explain complicated shit)
There's not a lot of reason to read Capital unless you're academically interested in all of the details therein; there are good summaries and explanations of that work that are less cumbersome and more relevant to our current time. I'm not saying people shouldn't read it, just that it's pretty dense and not really something that should be considered absolutely mandatory for understanding.
Much of what Lenin wrote, however, is a different story. State and Revolution, for example, is short and easy to read and understand. Even someone who has trouble reading could finish it an afternoon, it's like 100 pages. Just reading 10-15 pages a day - which should be trivially easy - will have it finished in no time. It's hard to believe someone couldn't get through a dozen pages of it at a time unless they're very lazy.