The Inner Game of Tennis.
My tennis coach gave me his copy, from the mid 80s, which was tattered and had clearly been read many, many times.
It taught me so much about life, and how to be successful.
My tennis coach was also my life coach when I reflect back on those days. He grew up in south central LA, rode his bike to the closest tennis courts and sometimes as far as Beverly Hills. He'd wait outside the courts until someone came along and ask if he could play.
He turned that into a full ride scholarship for tennis, became a senior level member of a huge telecom and then left to coach tennis to give back to the sport that gave him so much. He credited this book for teaching him how to focus on the important elements in life and most of all, the grit required to succeed.
Anyways, it's a great read. I haven't read the revised edition but I'm sure it's just as compelling.