The Stars, Like Dust - serialized in Galaxy January to March 1953 as "Tyrann."
[summary/review quoted from South Bend Tribune - from inside flap of the first hardcovers]: "The Earth had been made hopelessly radioactive and useless by atomic warfare, but young Biron Farrill, a student at the University of Earth, nevertheless found himself involved in a struggle that was worse because of the mystery in it. His father, on another planet, had been murdered and the young man himself was marked for violent death. The only certainty was that his pursuers, whose identities were unknown to him, were agents of would-be conquerors of everything and everybody in the galaxy. But young Farrill had to find out why he and his father had been marked for destruction. How he fought and what he found out while he even went into the blackness of a nebula to save himself makes a suspenseful story."