Napoleon Hill on two occasions wrote extensive memoirs about his life, starting with his youth in Wise County, Virginia, and ending, apparently, during World War II. I say "apparently" because the archives of the Napoleon Hill Foundation contain these two manuscripts, but they are obviously incomplete and end in the 1940s. Mr. Hill died in 1970. His last book, Grow Rich with Peace of Mind, was written in 1967 and sheds some light on his later years; but his own journals and memoirs of those years, if they ever existed, have not yet been found. The two memoirs were titled by Mr. Hill, Wheel of Fortune and Hand of Destiny. They contain details of his life, including his four marriages, two divorces and one annulment, which we at the Foundation have not seen in any of his other writings or speeches. They also contain many details about his successes and failures in business and there were more failures than successes, as he readily admits. The memoirs contain thoughtful insights into the state of mind of this great thinker—how he dealt with failure, profited from defeat, turned adversity into advantage, and ultimately achieved happiness with his last wife, Annie Lou, happiness which had eluded him for most of his life. Mr. Hill has said that the Master Mind principle, in which two or more minds work harmoniously to achieve a common goal, is the most important of the seventeen principles of success he studied during his decades of research into how people attain happy and successful lives. One of the many interesting stories in the memoirs is about how he and his third wife, Rosa Lee, used the Master Mind principle to discover the only one of the seventeen principles that no one had understood or realized before, Cosmic Habitforce. The Trustees of the Napoleon Hill Foundation® have combined the two memoirs into one, editing out repetition and putting events in chronological order where it made sense to do so. They chose to title the combined memoirs Master Mind, in recognition of the importance this principle played in his philosophy and life, and as a tribute to the mental giant who was the greatest thinker and writer ever in the fields of personal achievement and self-improvement.