Finished it today.
This is an odd one. If it was not written by Stephen King, I'd say this is a fair horror novel, even rather good, written by a guy heavily influenced by H.P. Lovecraft, obviously.
The first 250 pages (almost a short novel itself) or so aren't even a horror novel. There is no horror in it, it's a kind of portrait of the early Sixties in a rural god fearing American community. As that, it's a bit flat. It reads easy, but no catching atmosphere really, no deep psychological insight and so on.
Then the "horror" creeps in. And it's a very lovecraftian one. There is an ominous "other world" with unspeakable, unnameable creatures crawling around and somebody working very hard to open a door to this other world. Finally the door is opened and the horror revealed and it is ... ridiculous. Very, very flat, boring, nonsense. This is supposed to scare somebody? I don't get it.
So I don't know. For a Stephen King novel it's mediocre at best, like most of his recent novels, I'm sorry to say. Either he has lost his juice or he had plans with that novel that I don't fully understand.