The Border by Robert McCammon

 I've read some McCammon, back when I was younger and reading more Horror, and that was good--sometimes only pretty good, sometimes very good; this sits somewhere near the top of that range. It's hard to imagine a truly post-apocalyptic novel that's truly hopeful, but this at least mostly manages it: The novel has powerful, utterly alien things in it, but it's at its heart a novel about human perseverance and human faith winning the day. The victory is ... not about destruction, though it's simultaneously very destructive, thought about differently--though that destruction is something like a cauterization. There are clearly things in this novel that work the way they do because McCammon wants them to, there's no reason to believe physics bends those particular ways, but this is much more a novel of Fantasy or Horror than SF, alien invaders from beyond the stars notwithstanding. The story itself is pretty well-told, there are some POV choices I'm not really fond of--some head-hopping, a POV characters who changes but in ways that don't always convey well in narration--but McCammon does seem to grasp at least most of his human characters well, and his prose is solid enough.