"The Greatest Salesman In the World" is a self-help book written by Og Mandino. It tells the story of Hafid, a poor camel boy who becomes the greatest salesman in the world through the guidance of a wise mentor. The book is divided into ten scrolls, each containing principles and lessons for success in sales and life. It emphasizes the power of positive thinking, persistence, and the importance of developing good habits. The book aims to inspire and motivate readers to achieve their goals and find success in their personal and professional lives.