So what if someone set us up the bomb, or several bombs, and instead of nuclear winter and all the survivors dying of cancer, they got fused to each other and bits of glass and animals and broken doll heads? Pure is a horror story about atomic detonations gone wrong. Yeah—if that isn’t a terrifying thought, I don’t know what is. Julianna Baggott postulates a post-apocalyptic world that is the fevered vision of a…