Dale Carnegie's 1936 classic is the foundational text on interpersonal skills. It argues that the ability to deal with people is the single most important factor in business and personal success, and that this skill can be learned through specific, repeatable principles rather than personality or charm.
The book is built around one core insight: criticism is futile and dangerous. It arouses resentment, wounds pride, and makes the other person defensive. Carnegie shows that people respond far better to sincere appreciation and a genuine interest in their point of view.
The principles are grouped into sections on handling people, making people like you, winning people to your way of thinking, and being a leader. Each principle is illustrated with stories from Carnegie's experience teaching thousands of adults and from historical figures.
Worth returning to for the concrete techniques on listening, giving honest praise, and letting the other person feel the idea is theirs.