How to Win Friends and Influence People — Carnegie (1936)

Dale Carnegie's How to Win Friends and Influence People (1936) has sold 30 million copies and remains the foundational text of interpersonal effectiveness literature. Its principles — genuinely listening to others, remembering names, never criticising directly — are grounded in a deep understanding of human psychology that predates the behavioural science literature that would later validate them. Warren Buffett credits it with transforming his life.