Per Jacobsen’s new novel 25 Days brings horror to the holidays

Per Jacobsen. // Photo by L.C. Photography

Halloween is over, and even before the last jack o’lantern was extinguished, holiday décor was finding its way into stores. What’s a creepy kid to do when the other holiday season is in full swing?

Thankfully, if you’re the sort to have a “Every Day is Halloween” patch on your jacket and you’ve already started playing The Nightmare Before Christmas and Silent Night, Deadly Night on repeat, Danish author Per Jacobsen has you set with his new novel, 25 Days, out now from Atria Books. It’s a holiday horror advent novel, with each chapter taking place on the 25 days leading up to Christmas.

In it, “Hoping to bring his family closer together, Adam Gray arranges a vacation in a remote cabin on a snowy mountain. Things take a dark turn, however, when someone starts leaving gifts in the Christmas stocking mounted on the barn door. Each morning brings something new, and with every passing day, the contents become more terrifying. Soon, the family makes a spine-chilling realization: They’ve been dragged into a deranged game of Secret Santa, and if they want to survive, they will have to fight.”

It’s a thrilling, chilling (both literally and figuratively) run through the snow of the Danish countryside, and we were beyond excited to speak with the author about 25 Days.

Image Courtesy of Per Jacobsen

The Pitch: What made you want to write a Christmas horror story?

Per Jacobsen: It all began when my wife and I started tossing around the idea of me writing a horror story set during Christmas. She’s a fan of the genre and believed there was an appetite in the horror community for something festive with a sinister twist.

I liked the idea, but I wasn’t keen on diving in unless I had a strong concept to build on, and all I really had at the time was a vague mental image of a Christmas stocking dripping with blood. Then, one morning, it hit me: What if the horror story was told as an advent calendar? Twenty-five days, twenty-five chapters. That felt intriguing, and I quickly got to work. It turned out to be a fun, albeit challenging, way to plot and write.

There are so many little details about the family dynamic, location, and villain that really enrich the story. Where did the initial spark come from?

Well, as for the setting, that’s fairly easy to answer. I grew up in Denmark but have lived in Spain for the past eleven years, and, before writing 25 Days, we had just brought a group of our Spanish friends with us on a vacation to Denmark in late December. And it just so happens that we stayed in a vacation home with farm animals. It snowed while we were there, so… I can’t deny that some inspiration was taken from that place.

Regarding the family, it was very important for me that their dynamic and their individual developments throughout the story were present. On the surface, this is a horror story, but the “real” story is the one beneath: the story of a father trying to bring his family together—and the story of what it will take from each family member to do that.

25 Days gradually ramps up until it’s running full-tilt. When did you decide to just go full-out bonkers?

Once I knew that I wanted to go with the advent format, I spent some time thinking about the best way to structure it. It was very different from a “normal” novel in the sense that you’re locked in terms of time, date, chronology, etc. So, I made a set of rules for myself—and one of those rules was that it had to keep escalating all the way to the end.

The chill of the snow absolutely infuses every aspect of 25 Days. Do you have any winter experiences that informed this?

You could say that, yeah. I grew up in Denmark, where winters are cold and white. So, when I was a kid, there were days when school was cancelled, and we’d spend the entire day playing outside in the snow. Sometimes, we’d stay out there so long that our fingers would go numb and our lips would turn blue.

Those are, of course, happy memories… but there were also moments when we felt a stab of panic if we had stayed out a bit too long and had to run home while darkness fell over the snowy landscape. And those were some of the old emotions I pulled up while writing this story.

How did you come to decide to leave the villain so mysterious as to his motives? It’s utterly terrifying to know next to nothing of them.

That was first and foremost a consequence of the format. Writing a story that allows for only one chapter and viewpoint per day is pretty limiting, and I quickly realized that if I wanted to give each of the family members their own arc—which I did—I’d have to compromise somewhere else. Otherwise, there simply wouldn’t be room for it. Had I included the bad guy’s backstory, it would have taken away from what I consider the real story. And, as I’ve already mentioned, it’s about a father’s attempt to bring his family back together by taking a trip out to a place where they have nothing but each other to rely on. That was my starting point and my guiding light throughout the story. I wanted to make every family member realize that they would have to change in some way—both in order to survive and in order to become a united family again. So, I decided that their external experiences in this nightmare should be a symbolic representation of their changes on the inside.

That’s the short explanation of why I chose not to dive deeper into the mind of our big baddie. That said, it’s not impossible that I might do just that in a future release.

What projects do you have in the works?

Well, I can’t talk too much about it at this point because a lot of it is still secret, but I will say that a bunch of interesting things have happened over the past year—and next year looks like it might be a big one for me. So, that’s pretty exciting. Vague, I know, but exciting.

What I can talk about are my planned books. Anyone who has followed my career will know that I publish two books a year… and I’m almost done with one of the two for 2026. And I think my long-time fans will be extra happy about this one.

Per Jacobsen’s 25 Days is out now from Atria Books.