Lucifer's Hammer by Larry Niven and Jerry Pournelle torrent

The gigantic comet had slammed into Earth, forging earthquakes a thousand times too powerful to measure on the Richter scale, tidal waves thousands of feet high. Cities were turned into oceans; oceans turned into steam. It was the beginning of a new Ice Age and the end of civilization. But for the terrified men and women chance had saved, it was also the dawn of a new struggle for survival--a struggle more dangerous and challenging than any they had ever known....

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