James Blish's galaxy-spanning masterwork, originally published in four volumes, explores a future in which two crucial discoveries - antigravity devices which enable whole cities to be lifted from the Earth to become giant spaceships, and longevity drugs which enable their inhabitants to live for th...

James Blish's galaxy-spanning masterwork, originally published in four volumes, explores a future in which two crucial discoveries - antigravity devices which enable whole cities to be lifted from the Earth to become giant spaceships, and longevity drugs which enable their inhabitants to live for thousands of years - lead to the establishment of a unique Galactic empire.