"Who Moved My Cheese?" is a self-help book written by Spencer Johnson, M.D. The book uses a fictional story to illustrate the importance of adapting to change in both work and life. It revolves around four characters who live in a maze and rely on cheese for their happiness and success. When the cheese they depend on disappears, they must learn to embrace change and find new sources of fulfillment. The book offers valuable insights and strategies for dealing with change, overcoming fear, and achieving personal and professional growth.