Bargain @ $1.99 in the US only from Houghton Mifflin Harcourt's Mariner Books imprint, probably just until tomorrow, since HMH tends to rotate their sale offerings monthly (should be the same price at the usual other retailers):
The Crack in Space by the late Philip K. Dick (
ISFDB,
Wikipedia), his vintage parallel universe science fiction novel originally out in 1966 from Ace Books. ISFDB notes that the story is apparently an expansion of something called “Cantata 140”.
When a repairman accidentally discovers 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?