AN ENTIRE OCEAN separated Neil Gaiman and his new bride, and so he sat to scribble her a little something. He would write her a heartfelt short story, he reasoned, from perhaps the loneliest newlywed in the world.

Only it didn’t stay a short story. As Gaiman’s pen flowed with his torrent of feelings, the short story grew to a novella and then, after nearly six months, Gaiman had written — rather unwittingly — his first adult novel in eight years. The beloved and best-selling British author will be at George Washington University’s sold-out Lisner Auditorium on Friday night to discuss the creative watershed, “The Ocean at the End of the Lane,” which was released this week.

“It was a short story that didn’t stop — it’s never been like this,” Gaiman says, recounting how he began writing what became the novel in January 2012, while his wife of a year, American indie singer-songwriter Amanda Palmer, was in Australia working on her latest album.

“It’s a very personal book, for Amanda, and intentionally so,” Gaiman says. “And then at some point, I realized that in doing something very personal, I’d done something universal.”

The tale is fantasy, laced with elements of fairy tale and horror, but the starting line is derived from fact. Riding in a Mini sparked Gaiman’s memory that when he was about 7, back in Sussex, England, his family owned the same vehicle. He asked his dad what had happened to the car.

It wasn’t a happy answer, it turns out. A lodger in the Gaiman home, burdened by his heavy gambling debts, had stolen the car and asphyxiated himself. Armed with that story, the acclaimed author, 52, had an opening for his book, as an unnamed middle-aged narrator returns to the otherworldly rural Sussex lane of his boyhood.

“I stole the landscape particularly from my childhood, and I stole my viewpoints,” Gaiman says. “But the kid isn’t me.”

With its child’s vantage point on parental control and cruelty, the power of imagination and friendship, and perceived horrors, magnified, “Ocean” taps some of the same groundwater as Gaiman’s children’s tale “Coraline” (which spawned an Oscar-nominated film) and nods to some of his other titles, including “The Graveyard Book” (which director Ron Howard is working on adapting to film).

A connection to his earlier work, in fact, led to Gaiman approving a film of “Ocean” to be directed by “Atonement’s” Joe Wright, whom the author knew through Focus Features, which distributed “Coraline.”

“I didn’t want this being a big Hollywood picture, and I didn’t want a big Hollywood director, and I didn’t want a $150 million movie,” says Gaiman, who has amassed Eisner, Hugo, Carnegie and Newbery, Nebula and Bram Stoker prizes for his writing. “Something could go wrong . . . so I gave it to Joe.”

It’s fitting that Gaiman wanted to keep this on the smaller scale. The entirety of “Ocean,” he notes, takes place within a mile and a half of a tiny lake. “It’s the smallest thing I’ve ever done in [terms of] location,” he says, “but it goes to being the end of the universe.”

Amid the book’s sliding sense of scale and proportion, at least as told by the story’s 7-year-old guide, Gaiman plays with our sense of reality. “That’s the wonderful thing about a narrator,” he says. “You’re able to say things that can be true and not true at the same time.”

“Ocean” comes during a particularly creative peak for Gaiman. This year also includes the publication of two children’s books (“Chu’s Day” and “Fortunately, the Milk”); his commencement-speech book (“Make Good Art”); the airing of his latest “Doctor Who” episode (he plans to write a third); a radio play of his “Neverwhere” airing on BBC; Michael Sheen’s upcoming reading of “Ocean”; and his work on adapting his 2001 novel “American Gods” for HBO.

“It’s never been like this,” says the “Sandman” author. “I’ve never even begun [to have] something like this. . . . It’s barking madness, and nothing is movable.”

Yet Gaiman attributes this latest creative outburst to his wife and to not writing for a while and enjoying her performance-oriented world.

Given that Palmer — and the muse of loneliness — sparked “Ocean,” what does she think of this deeply personal book? She blogged this week that she didn’t get its full meaning — until Gaiman finally took pains to explain it to her.

“Neil started crafting a string of words that was like a long hand reaching out of his heart and across the void that I’d put between us,” Palmer writes on her blog. “I didn’t understand that, then. I only see it now.”

She sees now that Gaiman helped her traverse the pond that became their ocean — and the short story that became their novel.

VIDEO: To view an animated interview clip with Neil Gaiman, click HERE.