A novel of three several parts: a self contained City, an open community & a voyage amongst the stars. I found the initial part set in the City of Dispar to be the most intriguing section, featuring many classic SF wonders for 1956. Some great concepts of virtual reality, computer simulation, human storage & regeneration, along with moving walkways, domes cities & robot assistants.
Despite it's far-far future setting, once Alvin (not a very SF name is it) leaves the City it becomes a simple tale of exploration & discovery.