"Cities in Flight" is a remarkable and epic four-volume cycle of novels that follow space-faring humans from their first tentative rocket-powered journeys to the planets of our own solar system to the end of the universe itself.
The first volume introduces us to a near future which is about to be revolutionized by two key discoveries that will enable man to venture out into space en masse. The second volume follows one young man suddenly thrust into the "Okie" culture in which entire cities fly from planet to planet looking for work and raw materials (those of you who have read "Execution Channel" by Ken MacLeod may find this concept familiar). The third volume follows the decline of the civilization in which the "Okie" cities operate. The fourth volume continues beyond the decline of civilization to the end of time itself.
What's impressive is the way in which Blish manages to project his ideas about the life cycle of cultures and civilizations while still making it clear that cultures and civilizations are always composed of living, breathing individuals. In the first volume, there are three key characters who give us a vantage point to understand the declining western culture and the two key scientific discoveries that make possible the birth of the new culture of space pioneers. In the second volume, we follow a young man who is swept up ("press-ganged") into an "Okie" city, and through him we learn about the emerging "Okie" culture. Towards the end of the second volume, we are introduced to John Amalfi, the mayor of the space-faring city of New York, New York, who is the main character of the third and fourth volumes.
The omnibus edition I read includes an afterword that ties the timeline of the volumes to historical civilizations and compares them to the "Okie" civilization. Even without the afterword, this is a well-crafted exploration of culture and civilization with heavy references to our own Earth-bound history, and stands the test of time incredibly well. Well worth a read.