The Most Powerful Skill of Reading People: From Understanding Oneself to Analyzing People's Hearts

I'm curious whether Patrick King drew from personal experiences or research to develop these techniques. What motivated this approach?

Some methods seem so simple yet require mindfulness to implement regularly. Did others notice a difference when trying these tips in real life?

With so many non-verbal signals and subtle behaviors, I'm wondering how the author prioritized which ones to teach readers to recognize.