This new book by Farnam Street covers the first 9 mental models that we refer to as the General Thinking Concepts. A thorough understanding of these will improve the way you approach problems, consider opportunities, and make difficult decisions.
The Great Mental Models is a project by Farnam Street to help equalize opportunity in the world by making a high-quality education free and available to everyone.
Their newsletter is one of my favorites. Always super thoughtful and thought provoking. You can sign up here.