“In theory, this should be a great place to write, but some places are too pretty,” he said during an interview in the snug living room of his centuries-old cottage, which is generously proportioned for a hobbit, with a ceiling that barely exceeds six feet. “In practice, it may be a great place to have tea and cake.”

Before Mr. Ishiguro got around to talking about the inspiration for “The Buried Giant,” he digressed for nearly an hour about France after the Nazi occupation, modern-day Bosnia and Japan, and other places that seemed like possible settings for the novel at one point.

“Now you see my problem,” he said, explaining why it took him so long to write the novel and why, even now, he finds it hard to describe the story’s origins. “For a long time, I couldn’t get going on this book.”

In a way, the fact that “The Buried Giant” is such a surprising departure shouldn’t be surprising at all. Over the past three decades, Mr. Ishiguro, who was born in Nagasaki and grew up in England, has consistently bucked expectations, reinventing himself with each book.

After exploring post-World War II Japan in his first two books, he wrote his Booker Prize-winning novel, “The Remains of the Day,” which was narrated by an English butler. At the time, he worried that he was treading on familiar ground, but reviewers took the opposite view.

“I was afraid that people would say, ‘Oh, it’s the same book again, about an old guy looking back over his life with regret when it’s too late to change things,’ ” he recalled. “Instead, they were saying, ‘Your books are always set in Japan; this is a giant leap for you.’ I get this with almost every book.”

That pattern has repeated itself with each of his subsequent novels. “The Unconsoled,” a surreal, dreamlike novel about a pianist in an unnamed European city, was treated as magical realism when it came out in 1995. Critics and scholars classified “When We Were Orphans” as a detective novel. His 2005 novel, “Never Let Me Go,” was canonized as futuristic science fiction, although it was set at an English boarding school in the 1990s.