Christian fiction at its very best.
Peretti doesn't make the mistake that a lot of other Christian authors make. He doesn't ever stop telling his story to preach some valuable theological lesson. Rather he weaves it seamlessly into the narrative. The overarching theme of this book is "the power of prayer". But the story is straight out of a Stephen King novel. A small town is under attack from dark forces, both in this world and in the spiritual realm. The story is told from the points of view of humans and their angel protectors. Truly fascinating. Even if you think Christianity is a farce, this book still stands on its own.
I will also say that the sequel "Piercing the Darkness" wasn't nearly as good.