As a child, Nigerian-born British author Helen Oyeyemi had a habit of altering the endings of the books she read. “I started off changing bits of Little Women,” the 36-year-old admits by Zoom from Prague, where she’s lived since 2014. “I would actually write inside the book and be like, ‘No, that’s a lie.’ ”

In Oyeyemi’s version, Beth lived and Jo and Laurie got together. “I improved them!” she says, laughing. And then at some point, her writing “suddenly became stories that I hadn’t read anywhere.”

Oyeyemi’s seventh novel, Peaces, will be released by Riverhead Books in April. It, too, is something entirely new.

As Peaces begins, Otto and Xavier Shin are given a “non-honeymoon honeymoon” on a train by a beloved, wealthy aunt in honor of their commitment to each other. Off they go from southeast England along the “Lakes and Mountain Route”—“just imprecise enough to stir my interest,” notes Otto—accompanied by their baggage (literal and metaphorical, including the remnants of all their relationships past) and their pet mongoose. But the destination is not the point.

Once aboard the train, which is called the Lucky Day, strange things start to happen, particularly after they meet the train’s owner, Ava Kapoor. Does Ava need their help? Does she need them to leave her alone? Does she need something else entirely?

Add to the mix three people who are both there and not there, and you have all the makings of an Oyeyemi novel: disconcerting, captivating, disorienting, yet somehow grounded by universal questions about what makes us human. For instance, how do relationships change us and continue on, whether we’re aware of it or not? Who is seen and who is not seen, and who gets to decide that? What are we after on this odd journey of life and love that may or may not involve train travel?

Throughout Oyeyemi’s substantial career, her name has become synonymous with a kind of surreal horror, an ability to merge the creepy with the fantastic and magical, layered on top of myth and folklore that feels familiar, even if her versions are anything but. Her first novel, The Icarus Girl, published when she was 20 (she wrote it in high school), was a ghost story about an eight-year-old torn between identities. She followed that with two plays about the pain of life and death (completed while she was studying social and political sciences at Cambridge). She then published a string of novels: The Opposite House, inspired by Cuban mythology; White Is for Witching, which brought out comparisons to Edgar Allan Poe; Mr. Fox, a take on the story of Bluebeard; Boy, Snow, Bird, a loose retelling of “Snow White”; and Gingerbread, which finds inspiration in the story of Hansel and Gretel, as well as What Is Yours Is Not Yours, a collection of short stories connected by the idea of keys.

Peaces is about, well, love. “That’s a slightly terrifying thing to me,” says Oyeyemi, who admits that in her spare time, she’s a little bit obsessed with Korean TV dramas, or K-drama. “The thing about K-drama is that there’s a kind of special protected status that lovers have. It’s as if they’re in this kind of magic circle, and nothing can come in and harm them. Obviously, there are tests for their love, but as long as they stay steadfast, they’re going to be okay. And I think that might just be some underlying principle of the universe.”

Oyeyemi was also influenced the work of Barbara Comyns, a British author who combined the grisly with the beautiful in her retellings of fairy tales. (One of Comyn’s novels, like Oyeyemi’s, is titled Mr. Fox.) “All of her twists are twists of perception that are beneficial, or for the better,” she says. “It’s as if she decides that life is actually horrible enough, and in her fiction, she tries to find another solution. I think that that’s kind of translated into my own sense of narrative. At points, it was as if the story wanted to become kind of chilling, but it was almost as if the characters were just refusing that.”

Still, Oyeyemi couldn’t help wanting to mess with Otto and Xavier a bit, in part to work out some of the tensions in her own personal life. “They’re on this honeymoon, and I had at that point just completely given up on finding anyone,” she says. “So it’s like, ‘Oh, you guys have found your one? Well, I’m now going to punish you.’ ”

It didn’t quite work out that way. “Ultimately I just couldn’t be as mean to them as I thought that I would be,” Oyeyemi notes, though “they did get beaten up.”

Peaces started with a train and a title. For Oyeyemi, train stories, like Murder on the Orient Express, are connected to mysteries, as well as to some kind of crime that’s been committed and the need for retribution. “With this particular one, it felt like everyone on board was a criminal, but they weren’t sure whom exactly they had committed a crime against, or whom they had sinned against,” she explains.

And here’s where the story gets the Oyeyemi twist: “I was thinking a lot about, what if the person you broke up with hadn’t actually broken up with you? What if they didn’t accept your breakup, throughout this duration that you thought you’d left them long behind and found your worth? What is the existence of that relationship, and to some degree, that person? So, there’s a mystery to that.”

Peaces as a title also evokes “the idea of peace as a sort of lull between battles: that’s why they’re all pieces, because there’s no continuous peace,” Oyeyemi says. “And that was specifically in a relationship context, because you have this couple who were like, ‘This is the one. All my past relationships didn’t count. They were just part of the journey towards the one.’ ”

It takes Oyeyemi “about as long as it takes to have a baby” to produce one of her novels. “I do maybe four months full on, then take a month off, and then do another four months.” Before she begins, she has to prepare herself for what she calls “going to the cave.” She alerts everyone to what’s happening, then shuts off her phone. No one but family can reach her, and, even then, at a delay.

“It’s sort of like being dead for like a month, because nobody sees or hears from me,” Oyeyemi explains. “It’s very hard to write that intensely with having no life. I think it’s good, but it’s also scary, because you feel very alone when you’re doing that.”

So have Oyeyemi’s feelings about being alone versus being coupled changed since she’s finished Peaces? “Probably enough to not write another relationship book, for a long time, anyway,” she says. “I’m quite dismayed, because I was going to smash all of these people. But no, it was... I guess I just believe that you can make it through anything together. I have that kind of sense.”

Jen Doll is the author of the YA novel 'Unclaimed Baggage' (FSG) and the memoir 'Save the Date: The Occasional Mortifications of a Serial Wedding Guest' (Riverhead).