John Wyndham 
The Chrysalids 

The inhabitants of post-apocalypse Labrador have vague knowledge of the “Old People, ” a technologically advanced civilization they believe was destroyed when God sent “Tribulation” to the world to punish their forebears’ sins.

Now the inhabitants of this new world practise a form of fundamentalist Christianity. To follow God’s word and prevent another Tribulation, they must preserve absolute normality among the surviving humans, plants, and animals—and therefore practice a brutal for of eugenics. Humans with even minor mutations are considered blasphemies and either killed or sterilized and banished to the Fringes, a lawless and untamed area rife with animal and plant mutations. But there may be hope for this dark civilation in the form of a new set of human mutations…

A classic science fiction novel by the author of The Day of the Triffids and The Midwich Cuckoos.