Influence: The Psychology of Persuasion, Robert B. Cialdini

When I Stop Talking, You'll Know I'm Dead: Useful Stories from a Persuasive Man, Jerry Weintraub, Rich Cohen

How to Have Confidence and Power in Dealing with People, Leslie Giblin (I personally prefer this one over How to make Friends & Influence People)

The subtle art of not giving a f*ck, Mark Manson

Managing Oneself (Harvard Business Review Classics), Peter F. Drucker

Think & Grow Rich, Napoleon Hill

The Power of Habit: Why We Do What We Do in Life and Business, Charles Duhigg

The Way of the Superior Man: A Spiritual Guide to Mastering the Challenges of Women, Work, and Sexual Desire, David Deida

The Book of Pook (free)

Mystery Method (you might reread this one a couple of times, on the start just for the methods, but after a while for the thoughts behind them)

The 50th Law, Robert Greene

If you have any suggestions or books that helped you in any way or form with confidence, let me know, very curious to see which books helped you.