I thought I had read “Harbor.” It was published in 2008, with the English translation out in 2010, so I conceivably could have read it years ago and forgotten. The opening was so familiar.

But I couldn’t remember anything beyond that, other than a sense that I had once finished a story about a girl and her father in a lighthouse and felt cheated by the ending.

It seemed unlikely that was this book, though. I love John Ajvide Lindqvist’s work. He is perhaps my favorite horror author, and wrote a novel I consider truly frightening and disturbing, no easy accomplishment. (“I Always Find You,” a post for another day.)

So I checked “Harbor” out of my library. I figured the worst that would happen was I would realize I had in fact read it already.

Once the opening event had played out, I read, “During the course of this story it will be necessary occasionally to jump back in time in order to explain something in the present. This is regrettable but unavoidable.” In fact this happens regularly. Fortunately, the departures are diverting. And the first one was so striking that it convinced me I hadn’t read this book because there was no way I would not remember such a thing.

That established, I settled into the unsettling archipelago of Domarö. Lindqvist built a world of secrets, and how it looks and how you move through it change with your level of knowledge. Protagonists Simon and Anders suffer this in different ways; Anna-Greta’s gradual coming around to sharing knowledge is justified, but barely.

Anders is aware he may be possessed, and I felt his desperation and frustration. When a man hides under a blanket like a child, you have to like him to want to keep reading, and I did. The how of the possessions is better explained than the why, and the weakening of the sea wasn’t resolved to my satisfaction either. Still, I wasn’t mad at spending 500 pages this way.

I believe in this world. The magical elements are credible, not incredible. The horror is not the jump scare sort, but rather of elements deeply wrong, pervasive, inescapable. Never has “Why not just leave?” “And go where?” made more sense.