Caves of Steel, The (1962 Printing)

One fourth of its population was dead. The rest had little time to live. A mass of interstellar matter had invaded the solar system, fling planets out of orbit and block off the sun. In that titanic disaster, Man had one small chance to survive: Appeal to an alien intelligence that might exist, and that might – or might not – care enough to help!
GALAXY magazine falls this distinguished story “a swift-paced, ingenious and meaningful exploration of our distant tomorrows.”