State and Revolution is essential reading for any Marxist, but you probably already knew that. Lenin also conveniently cites a lot of Marx and Engels to point the read towards some of their important political works. It's relatively short but also really dense, as an incomplete series of 6 pamphlets written between the February and October revolutions. You could fill an hour just discussing the implications of almost any two consecutive paragraphs from most of the book. You'll want to discuss it with comrades you trust and take careful notes.

Quick side note for some of the more challenging economic literature: it's better to read works like Wage Labour and Capital, and Value, Price, and Profit like scientific textbooks than like historical literature. I found myself writing equations in my notes for some of the chapters in Value, Price, and Profit, for example. The exact numbers matter less than the underlying quantitative relationships - and the power differential between the working and capitalist classes that these relationships imply - that Marx and Engels are trying to describe.