The one that made the biggest impression (and, hopefully, impact) on me was definitely The Power of Habit. tl;dr: on a fundamental level, habits of all sorts shape much of our days and lives. It's like setting up automation scripts — it takes some time, but makes your life better and easier once you do. And they're like a sharp knife — a powerful tool, but be careful not to cut yourself. Good habits make you do things right without any effort, bad habits will ruin you. The book shows you how.