Wage-Labour and Capital is an ideal place to start with Marx because it presents most of the same fundamental ideas that volume 1 of Capital spends 1100 pages developing, but it's 50 pages and was intended to be read by workers and activists rather than academics https://twitter.com/alyssakeiko/status/1274818389429682179

Like everything else Marx wrote it's available online free https://www.marxists.org/archive/marx/works/1847/wage-labour/ch01.htm

If you want to dig more into the ideas in Capital but 1100 pages of 19th-century academic writing in translation is more than you want to deal with, I think the Fine/Saad-Filho is a fantastic summary. There are PDFs out there, or Blackwell's will send it to the US for $11 shipped

Read Lenin. He's dead; he's not going to hurt you. I'd go right to The State and Revolution to start, even though it's a little longer and more broad/abstract than What Is to Be Done? Lenin is an exceptionally good writer so it's not really a problem

Real subversion talk: People reading Mao scares the Man more than just about anything. Every time someone picks up the little red book for the first time, some wraith-lord in a dungeon beneath Langley gets a horrible chill down their spine.

The actual title is Quotations from Chairman Mao Tse-Tung, it was millions of people's first introduction, and it's good enough for yours too. It's on http://marxists.org  like all the rest, but it's broken up into a bunch of quick hits so a paper copy is good for the bathroom

or you can just look at it on your phone. Mao was a pretty tremendous writer too but the little red book is a great place to start with him because if a quotation really grabs you, you can easily check out the source context.

Some professional revolutionary is going to see this thread and scoff at how basic it all is and all the important things I'm "overlooking," but you have to start somewhere and it can be intimidating unless someone says, hey, here are places you can start. So hey, here they are.