The Rapture of Canaan by Sheri Reynolds

Ninah has lived her entire life in the community established by her grandfather, the spiritual leader of the Church of Fire and Brimstone and God's Almighty Baptizing Wind. While the community shuns most modern temptations to be in a pure state when the rapture occurs, 15 year old Ninah and her prayer partner James discover the oldest temptation of them all. When the community begins to believe that her infant son has divine qualities, Ninah turns to her level headed grandmother for direction. The church practices are a little hard to swallow but watching Ninah negotiate this moral minefield makes an interesting enough plane read.