On May 5th, 1818, Karl Marx, hero of the international proletatiat, was born. His revolution of Socialist theory reverberates throughout the world carries on to this day, in increasing magnitude. Every passing day, he is vindicated. His analysis of Capitalism, development of the theory of Scientific Socialism, and advancements on dialectics to become Dialectical Materialism, have all played a key role in the past century, and have remained ever-more relevant throughout.
He didn't always rock his famous beard, when he was younger he was clean shaven!

Some significant works:
Economic & Philosophic Manuscripts of 1844
The Eighteenth Brumaire of Louis Bonaparte
The Civil War in France
Wage Labor & Capital
Wages, Price, and Profit
Critique of the Gotha Programme
Manifesto of the Communist Party (along with Engels)
The Poverty of Philosophy
And, of course, Capital Vol I-III
Interested in Marxism-Leninism, but don't know where to start? Check out my "Read Theory, Darn it!" introductory reading list!
So as a leftist that I think identifies with Marxist-Leninist ideology but that didn’t find the communist manifesto an interesting nor easy read (it was small but not really approachable) are there any books that you recommend? I’m no economist but I do like reading logical arguments as to why capitalism doesn’t work, or better said, doesn’t work for the good of the majority but instead for a small minority (for whom it works very very well)
Most books by Ha-joon Chang, especially 23 things they don't tell you about capitalism. Fun fact, Ha-joon Chang isn't a Marxist, he's a liberal, but his writing is still critical enough of capitalism that South Korea banned his books.
Anything on prolewiki's library are good reads as well.
For a broad look at the evolution modes of productions and how capitalism came to be there is this 60s textbook from the soviet academy of science, there even are a series of videos following the textbook by the finish bolshevik that is pretty good.