The Followers Series Book 1: The Cleansing

In a dystopian future run by religion, four girls are leading the revolution against their traditionalist society into a freer future. Over fifteen months of bloodshed, they not only learn about (and test) their own ideals and relationships, but the future of the world around them.
Cammie is newly of age, but only third in line for throne, trapped in the shadow of her twin sister's legacy as she searches for power.
Bry has spent her whole life in the shadows only to attain power opposite Cammie in the war that'll tear apart both of their Statelands.
Zere is trapped in the cruel capitol where status is dictated by religious beliefs, and she risks her life to finally see outside the city walls.
Anais has risen through the ranks of the city and must risk her new power as she struggles to save the remnants of her old life.