"The Currents of Space is an early novel by Asimov and one of the best from that time that didn't hinge up robots or Foundation. (Though it was later shoehorned/retconned into his universal chronology.) It involves a man known as Crazy Rik, who must recover his memory in order to stave off disaster. It's a tense and well-plotted story of subterfuge and espionage with a well-developed planetary society that's surprisingly diverse for its time. It's not one of Asimov's best-known works, but it's a good, worthwhile one. "