The Sirens of Titan

Malachi Constant, heir to the largest fortune in America and famous for gambling wins so improbable they read as cosmic favoritism, gets summoned by Winston Niles Rumfoord, a man scattered across space and time inside a chrono-synclastic infundibulum who can see Malachi's entire future in advance. Rumfoord tells Malachi he will end up on Mars, then Mercury, then Titan, and that he'll father a son with Rumfoord's own wife along the way, a prophecy Malachi resists exactly as hard as the novel needs him to in order to fulfill it anyway.

Vonnegut's actual joke, withheld until deep in the novel, is that Malachi's entire biography, his luck, his fortune, humanity's wars and religions and monuments, have all been secretly engineered by Tralfamadorians, a mechanically advanced civilization stranded across the galaxy that needed Earth's entire history nudged along in order to deliver a single spare part to their messenger, Salo, stuck on Titan. Every grand human achievement the novel name-checks, Stonehenge, the Kremlin, the Golden House of Nero, turns out to be an unwitting piece of interstellar semaphore relaying instructions nobody on Earth ever knew they were following. Rumfoord uses his own foreknowledge to found the Church of God the Utterly Indifferent back on Earth, a religion built explicitly around the premise that no cosmic force is paying attention to human affairs, which makes Salo's actual, very attentive engineering of those affairs the novel's blackest joke.

Vonnegut introduces Tralfamadore and its flattened, indifferent view of human free will nearly a decade before Slaughterhouse-Five made the planet famous, and the earlier version here is considerably more mechanical: these Tralfamadorians are literal robots serving a single bureaucratic errand, not the fatalistic philosophers of the later novel. Reading the two books together shows Vonnegut testing the same cosmic joke twice, first as science-fiction premise, later as the emotional architecture for a war he'd been unable to write about directly for over twenty years.