Science fiction's most philosophical talent here offers 24 stories, some of them landmarks in the field. "Gödel's Doom," for instance, attempts the difficult task of turning a classic mathematical problem into fiction, in the process meditating on determinism versus free will. In what is actually his most conventional piece, "Lenin in Odessa," Zebrowski enters the mind of Joseph Stalin to conjure an extraordinarily detailed alternative history. Some tales, though based on serious philosophical conceits, are like cartoons: in "Word Sweep," for instance, the words characters speak form in the air and crash to the ground, slowly filling up the world; and the wry "Stooges" features Curly of the Three Stooges. "Sacred Fire" is a wrenching consideration of violence as a necessary component of being human. "This Life and Later Ones" demonstrates how awful a man-made immortality might be. Zebrowski is outrageously didactic but so polished a stylist and so original that the reader is sure to be mesmerized.