Great! If you want to learn more about Dialectical and Historical Materialism specifically, my two favorite works are Elementary Principles of Philosophy by Georges Politzer, and Socialism: Utopian and Scientific by Friedrich Engels. The ProleWiki article on Dialectical Materialism is also quite good if you just want an overview, it’s a much faster read and will get you the general idea, but not the depth the other two sources would give.

I bring up DiaMat and HistMat specifically because of your statements here:

If you create human society and let it evolve in an un-constrained manner, there is a large probability that you will at some point pass through a period of capitalism.

This is not about it being “optimal for society” but is rather a meta-stable state that is easy to arrive at given a simple set of rules and initial conditions. “Human nature” refers to those rules and initial conditions. It doesn’t mean that it is a good thing, it is not unavoidable, and it is not likely to represent a global optimum or the final point in human society’s evolution.

The key inferences of Historical Materialism, oversimplified, are that each mode of production paved the way for the next. Capitalism largely arose from Feudalism. Over time, a bunch of quantitative shifts, such as improvements in technology, production, and buildup of wealth, result in qualitative shifts in the Mode of Production. The steam engine, for example, allowed factories to be set up in cities, focusing on commodity production and close living quarters, as opposed to being more spread out and largely agricultural due to being tied to the land. Capitalism is a very natural point to reach, but also has its own quantitative shifts that lead to Socialism overtaking it.

Human Nature, therefore, is malleable. It depends on the material conditions humans find themselves in, these structures and externalities are what drive change to new ideas, the old gives birth to the new. Capitalism is as much Human Nature as Socialism, as Feudalism, as Communism, as tribal hunter/gatherer societies, yet what was considered “human nature” has changed and will change yet again based on all of these modes of production.

As for history, this is a much deeper subject. If you have a specific subject you’d like to learn about, I can field some suggestions, but for a short and general historical contextualization of Socialism as it exists in the real world, there’s no better work I’ve found than Blackshirts and Reds. Dr. Michael Parenti isn’t so much a Marxist himself as he is a pro-Marxist. He supports Communists and Socialists globally, while not being some fifth-level grandmaster Marxist-Leninist. As a consequence, his writing is much more approachable for non-Marxists, and does a great job walking through why someone would support, say, the USSR, Cuba, etc while giving nuanced critique of the successes and failures of Socialism historically. His 1986 lecture is also a fantastic companion piece.

If you’ll forgive the tangent, I also want to point out that people often over-focus on the issues of ghosts. People love discussing if x event was justified, y person “good” or “bad,” z country “truly” Socialist or “betraying” socialism, but these aren’t generally as useful as studying history so as to discover what challenges and successes are universal or local to Socialism. Socialists tend to adopt the stance of trying to learn what works and what doesn’t work critically, while non-Socialists tend to boil all of Socialism down to purely the mistakes made by Socialist leaders, building up “legends” surrounding these figures in an attempt to discredit Socialism entirely. That can be why you find yourself seeing controversial claims, a large part of defending Socialism is defending it from the unjustifed attacks those opposed usually jump to, rather than the more useful critique of Socialism as it truly exists. You’ll find that the best critique of Socialism in the real world comes from Socialists, and we Marxists are not afraid of genuine critique. Rather, Marx himself advocated for the “ruthless critique of all that exists.”

With that all being said, that should be good to get your feet wet into theory if you want! If you prefer, I can also offer different recommendations on more specific topics in theory or history. I’m no expert, but I’ve read a good fair bit myself and as such have works I’m fond of, and ones I think you can save til later, if you so choose. Hope that helps!

One teeny tiny final note, I also like Why Marxism? as an introduction for why we should even study Marxism specifically. Roderic Day breaks down the importance of Marxism as a scientific framework useful for understanding humanity, how we got here, where we are going, and how to best take advantage of that knowledge.