I thought I might have read this before, but no, it's new for me.
I really like the imagery of Kingsport in the snow. There's a descriptive passage in there that is one of the most evocative pieces of writing I've ever read by Lovecraft. I'm almost sad to leave that part, and go into the building. I wish I could wander around the town as described and explore it more.
The household with the strange inhabitants is well described too, and there's a nicely growing sense of menace and unease there. Though for me this part goes on too long. I'm clearly still missing the town outside!
The same issue is a problem with the underground sections. I like the walk to the church, and descriptions of the throng of people who leave no footprints. But once things are underground it's less successful for me. And I find the description of the creatures particularly disappointing, though I like the part where the narrator dives into the river.
But I do like the time shift at the end, to a more modern Kingsport, and the idea that it may all have been a vision in the narrator's mind. Obviously I'll side with the no it all happened viewpoint. But it's a nice ending. I'd just like to see some of the earlier sections tightened up a bit, to my taste anyway.