Das Capital Volumes 1-3. Core theory on the basic nature of capitalism and familiarity in the core terminology among anti-capitalist nerds. You get to choose whether this counts as 1 or 3.
Imperialism: The Highest Stage of Capitalism by our good friend Lenin. Good for understanding the core ideas of imperialism and a verified theoretical extension to Das Kapital.
Blackshirts and Reds by our good friend Michael Parenti. A good overview of the 20th century that agitates for questioning dominant liberal media narratives on the nature and history of socialist movements.
Blood in my Eye (George Jackson). Good balance for understanding the internal colonization framework useful for the Black Panthers et al. Valuable for an American perspective in particular as well as challenging your own ideas on what counts as adventurism vs. valuable direct action. Also elucidating on the military-industrial complex and the ties between capitalism and anti-blackness.
Trans Liberation: Beyond Pink and Blue by comrade Leslie Feinstein. Comrade Feinstein exhibits a model for imperial core organizing that includes liberation struggle, is/was cool as shit, and was a member of a precursor to the PSL.
Superimperimpeeralism by Michael Hudson. A reasonable political economic argument as to the self-serving nature of US foreign policy, including its international financial and military tools.
Of course there's much more to read and talk about, but these are a good foundation for any imperial core commie.
Edit: Fanon, so hot right now. The Wretched of The Earth is required reading right now.
I tried to read it as a first book and it was way too dense for me. It's a book that needs a primer and background knowledge of the subject first
People have responsibilities and things going on in their life that make sifting through abtruse German philosophy a hard thing to devote the time to do. Capital is not a book I think is a helpful suggestion for a beginner
Disagree with Dad Kapital. That shit is way too dense for someone that needed a bet to read theory. Marx Madness or some other synthesis could be good, but I still find Kapital to be pretty unimportant for how hard it is to read. Kapital is pretty much communism's versions of mathematical proofs. There's nothing in Kapital that Lenin or Mao don't say in 1/10th of the time.
Speaking of shit that's way too dense Simalcra and Simulation by Baudrillard is fire. Bro definitely caught his pen on fire
If you don't read Das Kapital, you don't understand Marxism but are instead gleaning it from other sources that only partially cover it, generally for the purposes of their own applications. A lot of people do just go with Lenin or Mao and then constantly fuck up because they do not in fact live in conditions where there's a substantial peasantry or a monarchy. Once they realize this, they don't know what to do - how to "update" Marxism, as well as how to criticize it. IMO this is also why Trots and Gonzalites and so on can proliferate so easily. I have yet to see a Trot reading list that includes Das Kapital, but they all call themselves Marxists. A large number that I've interacted with don't even know the basics.
It's also not very dense, it's just tragically German. Once you get used to the writing style and maybe a little Hegel it's a fairly quick read. The real barrier, to the extent that there is one, is just to set aside reading time at all.
This is where I like Carlo Cafiero's summary of Capital. Endorsed by Marx himself! Yeah, Das Capital is literally a from-first-principles philosophical work, reading it is basically a semester worth of work
https://www.marxists.org/archive/cafiero/1879/summary-of-capital.htm