A novel about the last man on earth. Themes of profound loneliness and solitude, but also of freedom and clarity

Heya. I would like a recommandation for what is basically a post apocalyptic book, but completely devoid of action of any kind. Essentially it should be just a lonely person roaming around after the end of civilization. Free of any responsabilty or burden, with nothing left to lose or gain, he wonders. No interaction. No [...]