What book has had the biggest impact on your life?

What book has had the biggest impact on your life? I’ve been thinking about how certain books can completely change the way we see the world, our habits, or even our goals in life. Is there any specific book that influenced your thinking or personality the most? I’m also curious whether it was a fiction story, a self-help book, or something educational that left a strong impression on you. What lessons did you take from that book that still affect you today?