Philip K. Dick 
Crack in Space 

The discovery of mysterious gateway leads to a new world full of dangerous possibilities in this science fiction tale from an iconic author. When a repairman accidentally finds a parallel universe, everyone sees it as an opportunity, whether as a way to ease Earth’s overcrowding, set up a personal kingdom, or hide an inconvenient mistress. But when a civilization is found already living there, the people on this side of the crack are sent scrambling to discover their motives. Will these parallel humans come in peace, or are they just as corrupt and ill-intentioned as the people of this world?“Dick’s best books always describe a future that is both entirely recognizable and utterly unimaginable.”—The New York Times Book Review