I never thought I'd write a review like this about a Stephen King (and Owen King) novel, but here goes. First, I'm not going to give a synopsis of the plot, others have done so already. I'm more concerned about the writing, and maybe your experience. This was mine.
1) It could have been easily cut in half. I've NEVER had a problem with SK's book lengths - the larger the better for me. I like to enter a fully realized world from Mr King, but in this novel I always felt held back as if not to see to closely just how the machinations worked. That may have to do with there being co-authors. I couldn't say. This novel drags from the first page one and never recovers. I only finished it because i don't like to leave a book unfinished, no matter how bad I think it is - and not that this one is bad particularly, it just feels like I' was slogging though unfinished or an overwrought premise.
2) It seems like a re-tread of the concept SK posited in "Under the Done" with subtle eerie references Joe Hill's "The Fireman". BUT, with half the pages and twice the characters.
3) I've never read an SK book of any length where I wanted it to be edited more tightly, whole passages cut out for wandering too far afield, or just being plainly redundant. SK - on his own - is great at getting to the heart of his characters, even those you're NOT rooting for. It's just the way he writes. In this collaboration, it seems as if he's holding back. I won't posit why, but this seems like a good novella with a thyroid problem; it just keeps growing and growing and growing.
No one really stands out as an individual 'character'. They all sound boringly the same. All the marriages between the couples are toxic and after the Aurora plague hits, it seems the women at least get better shrift while the men go on being the asses they were at the beginning, only moreso. Though the women don't get a free pass either. Snarky and bitter would be putting their attitudes and characterizations mildly, even the ones we're supposed to be most sympathetic to or care about. There really aren't any characters who ARE sympathetic. The Kings rehash - ad nauseam - the same process of women succumbing to the Aurora ( Sleeping Beauty's name from the fairy tale, in case you don't get it the first five hundred times it's mentioned), and the town's male reactions (always bad and with ulterior motives).
There is not one single likable character in the entire 700 page book - except maybe the little fox that dashes in and out of the story. Maybe!