The Year of the Flood tells the story of two women connected by their involvement in a sort of survivalist cult of vegan pacifists called God's Gardeners. Toby was rescued from an extremely abusive man by the group and although remaining skeptical of some of their beliefs she becomes a stalwart of the organization. Ren is a young woman raised within the group who, although she later goes off on her own, never leaves their beliefs entirely behind. Toby is a strong but emotionally damaged person who has a very difficult time trusting others. Ren is a sweet caring person who has always relied on protectors in her life, which has left her particularly ill suited for surviving in a post-apocalyptic wasteland, which is where they both end up.
The book is a sequel to Atwood's Oryx and Crake, in which the Gardener's were mentioned in passing as a fanatical group of eco-terrorists. Atwood clearly spent a lot of time researching and developing her pacifist Earth friendly religion for the novel. She documents the details of their beliefs and practices, their festivals, dietary habits, ethics, and their drafted Saints including Rachel Carson and Diane Fossey. She even writes their hymns, which are included as poems in the book. The irony is that the group's belief that God will soon wipe away corrupt materialistic civilization with a "waterless flood" apparently inspires Crake, the amoral scientist from the previous novel, to create and unleash his engineered pandemic on humanity.
My only quibble with Atwood's writing is the impossible convenience with which characters from both novels keep running into each other. It is like they all live in the same small town with only a few hundred people and everyone knows everyone else. The connections between Jimmy/Snowman, the main character of Oryx and Crake, and the characters of this novel strain suspension of disbelief. I find it easier to believe in the genetically engineered pigs with enhanced intelligence than to believe that every woman who impacted Jimmy's life in the first book, from his runaway mother, to the girl he lost his virginity with in high school, to his roommate in college, to his last serious girlfriend before the pandemic, were all involved with a group of eco-fanatics that Jimmy knew nothing about.