Going to repost my recs from this comment:

1. Lenin's Electoral Strategy from Marx and Engels Through the Revolution of 1905: The Ballot, the Streets—or Both by August H. Nimtz is a wonderful book that I think is very important for our current moment. It explains how Marx, Engels, Lenin, and many other Marxists viewed electoral politics as a ground for propaganda and agitation, but not as a means to take power. That can only be done through a revolution, and therefore you must have an independent workers party to educate the masses. Helps cut through a lot of the "lesser evil" discourse around left-leaning spaces, and does so with a heavy dose of theory.
2. Caliban and the Witch: Women, the Body and Primitive Accumulation by Silvia Federici is a great book about primitive accumulation (building on Marx and Luxemburg) in the context of the early modern world, and how it laid the groundwork for (and continues to feed into) modern day labor exploitation. Very readable.
3. Fossil Capital: The Rise of Steam-Power and the Roots of Global Warming by Andreas Malm is my favorite book on here. It's a Marxist account of how the switch to burning coal over water wheels was predicated on labor control rather than anything to do with price, and demonstrates how the cause of global warming lie squarely in the court of capitalists, and not "humanity" or some other vague amalgamation of people. Really recommend this one

BONUS: The Origin of Capitalism: A Longer View by Ellen Meiksins Wood. Great account that builds on Marx to demonstrate how capitalism was not inevitable, but a historically specific development in 17th century England that relied on a very lucky coincidence of factors. Easy introduction to this very large and important topic.