Night Lamp by Jack Vance
Against the backdrop of the Gaean Reach, the widely populated region of space where the full diversity of human development is revealed, the story of Jaro Fath unfolds: from wildling orphan to spaceship captain, a tale of adventure and discovery wittily told.
Jaro's life is directed by an inner voice he cannot account for . . . until he returns to Kammerwelt, described in The Handbook of the Planets as the fourth world in the entourage of Robert Palmer's Star, drifting in a far-flung sector of the galaxy known as the Dragon's Maw.
Jaro is haunted by memories of his dead mother's terror, and he is about to find out why . . .