The Unlikely Pilgrimage of Harold Fry, by Rachel Joyce

When Harold Fry, retired and unhappily married, receives a letter from an old friend informing him of her cancer and imminent death, he writes her a letter and on the way to mail it somehow begins a 500 mile pilgrimage to save her.  On his walk, he meets many people who offer him food, encouragement, and their stories.  An utterly charming book.