Robert Silverberg - Shadrach in the Furnace

The year is 2012. The world lies ravaged by biological warfare, its population decimated by a ferocious genetically-transmitted disease known as the organ rot. And presiding over the ruins is a ninety-three-year-old tyrant, preserved in a state of youth by a series of organ transplants: the self-styled Genghis Mao. Shadrach Mordecai, Genghis Mao's trusted personal physician, was a vital cog in the great machine devoted to keeping the ruler alive: linked to him by a network of electronic implants, Shadrach was able to detect and diagnose the first signs of malfunction in his lord and master. But close as he was to the aging dictator, Shadrach could not have known that events would soon plunge him into a desperate struggle - a struggle in which a paragon of idealism faced the very incarnation of evil.