Howard Marks is one of my favorite writers on investing. This book is a compilation of many of his memos organized into 19 "most important" concepts. These insights are especially relevant today because of what is happening in the economy and the stock market.
Think and Grow Rich has been recommended by several friends and I read it in 2019 together with a mastermind group. It is no surprise that it is so popular and frequently recommended. It contains so much information, it will take several re-readings to absorb the content and put it all into action.
The most important message of the book according to the author, Guy Spier. Nothing matters as much as bringing the right people into your life. They will teach you everything you need to know.
The Richest Man in Babylon is written in story form; fun to read and easy to understand regardless of your financial education. It's a concise book and hard to put down once you start reading.
The key concept is "Money is plentiful for those who understand the simple laws which govern its acquisition."