What is the most effective self-help book you have read?

I agree, I thought it would be about being nice to people . It is more of a psychology book about how people interact . The most enlightening book I have read .

i mightve read that one too before but maybe i should read it again

The Gentle Art Of Verbal Self Defense.

Marie Kondo’s book. Changed my entire approach to owning things.

How to Win Friends has a lot of Confucian perspective.

Also, "The Greatest Salesman in the World" by Og Mandino;
"Jonathan Livingston Seagull;"
"The Great Divorce;"
"The Kindness Challenge;"
"The Quarter-Life Breakthrough:  Invent Your Own Path, Find Meaningful Work, and Build a Life that Matters;"
"For Couples Only;"
"Understanding Yourself" by Mark Prophet.