This 2011 novel by Sarah Rayne is wonderfully strange and gothic.
At outset, a reporter has a mission to uncover a mystery surrounding a family. He becomes compelled by the photographs that Simone Anderson displays at the Thorne gallery.
Somehow the journalist can detect Simone's dark secret:
"She had been four years old when she became aware of this inner darkness, and she had been a bit over five when she began to understand where it came from.
The other little girl, The unseen, unheard child whom no one else
could see or hear, but who lay coiled and invisible inside Simone's mind. Simone did not know her name so she just called her the little girl."
Some have referred this as a more grown up "Stranger Things." The kids in this series are in high school rather than middle school. Other than that, it shares many characteristics with the other series: a small town (this one in Germany), a government facility(a nuclear power plant), woods for kids to disappear in.
Louis Hofman (Land of Mine) stars in this series as Jonas Kahnwald.
In Iceland, there's a long tradition of giving books as gifts during the holidays. Iceland book gifting tradition is called "Jolabokaflod"
or "Christmas Book Flood."

Each Icelander receives at least one book during the Christmas season. Gifts are typically opened on December 24th. Icelanders usually spend the night before Christmas reading.
This is what I want to do this year. No regular gifts. Just books.
If you want to read more about Iceland, you may want to try these books:
Moss, Sarah. Names for the Sea.
https://guidetoiceland.is/connect-with-locals/aldasigmunds/the-icelanders-and-their-big-love-of-books