The Roadmap of Loss by Liam Murphy

It's 1997 in Melbourne, Australia, and Mark Ward is struggling to make sense of the world following the sudden death of his mother. His father, Dylan, had abandoned him and his mother when Mark was still a child, and Mark has always believed he died in a car accident shortly afterwards. For most of his life, he has carried an unjustifiable sense of guilt about his father's absence, overlaid with memories of him as a cruel and unloving man.
Clearing out his mother's house, a bereft, rapidly deteriorating Mark is shocked to discover a collection of letters written to her by Dylan - some of which postdate his supposed death. Discussing life and love, fears and dreams, set against the backdrop of his bohemian travels across the United States, Dylan's letters become beacons for Mark, who sees in them a final chance to achieve closure, as well as his own redemption. With a burning suspicion that Dylan may still be out there, Mark decides to retrace the journey taken by his estranged father twenty years earlier.
Moving through the country with only a beat-up car as company and the letters of a stranger for guidance, Mark is faced with the enormity and polarity of late nineties America. Bouncing from one city and bizarre situation to the next, he encounters a tapestry of people along the way - many of them eccentric, some malign, some nurturing, others as lost as he is. Alone in a foreign land, the search for peace soon becomes a battle with loneliness, addiction and nihilism as Mark begins to see in himself reflections of the father he grew up resenting.
Raw and uncompromising, The Roadmap of Loss explores human fallibility and vulnerability, the courage of letting go of the past, and the power of forgiveness.