"The Unlikely Pilgrimage of Harold Frye" by Rachel Joyce [1]

Harold Fyre is retired, henpecked, and indifferent to life.  Then he receives a letter from a elderly friend who is dying.  Rather than mail her correspondence Harold decides to walk 600 miles to deliver his message in person.  His trek is peppered with fascinating characters who help unlock Harold's buried spirit and renew his sense of life.