In a letter to himself on the IAAF site, Kipchoge raves about a book called "Who Moved My Cheese?"
the IAAF wrote:
Besides the great people you will go on to meet, you will also develop a passion for books, which will equip you with skills that will help your career. You are particularly keen on self-help books and autobiographies, and one book in particular – Who Moved My Cheese? – is a publication you’ll refer back to again and again. The book is just as relevant to a businessman or an athlete but is very helpful in helping you cope with periods of change.
Book is here:
https://amzn.to/313pdwZFull letter here:
https://www.iaaf.org/news/series/eliud-kipchoge-kenya-marathon-advice