The Handmaid's Tale is a frighteningly convincing story of a woman trapped in a fictional North American republic of the future, the Republic of Gilead, where religion is used by a group of Christians to reduce women to a few subservient roles stratified by class but limited in all cases to the function of procreation or domestic tasks. Dissenters, including people of other religious persuasions, were tortured and killed.
The Year of the Flood is set in a different fictional future after most of humankind has been wiped out by a"waterless flood" -- actually a pandemic-- predicted by Adam One, leader of a religious group called God's Gardeners who preached oneness with nature and taught its member survival skills to prepare them for the coming disaster. It is told mostly from the point of view of two survivors from God's Gardeners. Again, Margaret Atwood imagines convincing scenarios -- of genetic experiments gone awry and unchecked corporate power gone amuck.
In both stories, however, there is redemption. In The Handmaid's Tale, an underground resistance, a FemaleRoad, eventually rescues the woman. Not all Christians succumbed to the madness that was the Republic of Gilead. The Year of the Flood is ultimately a tale of survival by a few of God's Gardeners, helped along by unlikely friendships.
I highly recommend both books to encourage people to think about possible futures, especially possible horrible futures, so that we may try to avoid them! However, if you don't want to think of serious things, just read the books anyway, for entertainment.