The Clean Coder: A Code of Conduct for Professional Programmers

I personally don't like Clean Code, but understand that a lot of people I respect do. I do want to throw Clean Architecture into the ring though since we're in the topic. That book is a top three software book for me. It made me understand why OO is a thing and what concepts I should pretty much always use from that ecosystem. The concept of interfaces (not just the programming construct, but the general idea) was massive and it changed my view on the testability of code. Martin has some other good stuff related to professionalism as a programmer. He has a few talks and The Clean Coder and those are absolutely worth it as well.

This book when combined with "The Clean Coder", and "Refactoring: Improving the design of existing code" completely changed how I thought about programming. It "levelled me up" so to speak. Even though I'm as far from being good as it gets, I still know I improved significantly from reading these three books.