The Currents of Space by Isaac Asimov

Hardcover. Condition: Very Good, Dust Jacket: Good+. 1952. Doubleday. Book Club Edition.

High in their fortified city, protected by brutal mercenaries, the Sarkites live in magnificient luxury. Below them, in the eternal Spring of Florina, "the most beautiful planet in the Galaxy," the native Florinians labor ceaselessly in dire poverty to produce the precious kyrt fiber that brings wealth to their masters, the Squires of Sark. Suddenly there is a cryptic warning from space.

Book 2 in the Galactic Empire Trilogy.