Aphorisms, home-spun wisdom, and an unflagging belief in the public and private benefits of positive thinking turned Dale Carnegie's name into a household phrase that, since the 1930s, has been uttered with both gratitude and derision. Applying the lessons that he learned from what he perceived to be his failures early in life, Carnegie began to teach a course in 1912. Ostensibly a nonacademic, public-speaking course, Carnegie's class was really about coming to terms with fears and other problems that prevented people from reaching their full potential. Through word of mouth the course became hugely popular, yet Carnegie never stopped tinkering with the curriculum, excising portions that no longer worked and adding new material based on his own ongoing life experience. In 1936, he increased his profile exponentially by publishing How to Win Friends and Influence People, which ranks as one of the most purchased books...