Marx and Engels‘s historical analysis is breathtakingly, brilliantly simple. I think it‘s wrong but, again, you‘ve just got to admire its genius. Obviously, without understanding the historical basis of Marx‘s thought you can‘t understand anything else in Marxism.

The other one that had a really profound impact on me was “The Four Agreements“, which is basically the agreements that you make with yourself. People often have conflicting agreements in their mind and if you read this book you'll stop the chatter in your mind. It makes it way easier to focus and execute. It also makes you much stronger emotionally

Aristotle‘s Nicomachean Ethics was something I reread and cannot recommend highly enough.