The Year of the Flood by Margaret Atwood
God’s Gardeners live off the grid, more-or-less. They recycle, eat trash, eschew consumerism and products created by the corporate chemical-biological compounds. They are led by AdamOne, and they try to memorize the names of extinct (or soon to be extinct) species. They take in almost anyone, including our protagonist.
Meantime, a massive virus has wiped out most of humanity. Jimmy the Snowman and The Crakers, and a few ladies Jimmy once knew survive. Also some Painballers, which are pretty much exactly what they sound like.
This novel rounds out the world a bit, and introduces us to the brothers, Adam and Zed, who end up being pivotal to the early stages of the after-party.