É claro que tudo está na cabeça do protagonista, mas isso imediatamente me lembrou do Briefing for a Descent into Hell de Doris Lessing (1971). Coisas poderosas.
Do site da Lessing:
Professor Charles Watkins (Classics), doomed to spin endlessly in the currents of the Atlantic, makes a landfall at last on a tropical shore. He discovers a reined stone city, participates - moon-dazed - in bloody rituals in the paradisiacal forest, witnesses the savage war of the Rat-dogs and is borne on the back of the lordly White Bird across the sea of the dead. Finally, the Crystal claims him, whirling him out into space on a breathtaking cosmic journey.