In Paradise might seem to be an odd, perhaps even an offensive, title for a book set in a concentration camp. But it could have been even more provocative, remarks Peter Matthiessen, speaking of his new novel, which Riverhead will publish in April. “I was going to call it Dancing at Auschwitz,” he says. “That would have ruffled some feathers!”

Matthiessen has never flinched from challenging his readers. His nonfiction, such as In the Spirit of Crazy Horse and National Book Award–winning The Snow Leopard, makes a passionate case for preserving the world’s wild places and indigenous peoples; his novels, from Race Rock in 1954 to Shadow Country, another National Book Award winner, in 2008, explore extreme aspects of human experience. But Matthiessen never aims simply to shock; the discarded title for In Paradise refers to a mysterious event that occurred during a meditation retreat that the author attended at Auschwitz in the 1990s. In the novel, as in real life, the participants join hands and begin to move around the camp mess hall in a circle, singing. They are “transcending the atmosphere of grief and banishing lamentation,” thinks protagonist Clements Olin. “Horror penetrates our bones, but at the same time there is joy,” says another character.

“We were all baffled by it afterward,” says Matthiessen. “A few people got angry.” They thought it was disrespectful to those who had suffered and died there, he notes. But, the author adds, “I felt very powerfully moved by the dancing; it lifted me right out of the blackest gloom. That’s what made me want to write this novel: how does this happen?”

The title finally chosen comes from an older version of the gospels with an alternate version of Christ’s response to the thief being crucified with him, who begs to be taken to paradise. Instead of answering, “Thou shalt be with me this day in Paradise,” Christ replies, “We are in Paradise right now.” As Clements Olin sees it, that means, “Everything right here at this moment, Paradise, agony, and God.”

“That would be the Zen position,” comments Matthiessen, himself a Zen roshi (master teacher) who still gives classes at the meditation hall he established on the grounds of his home in Sagaponack, Long Island. “And Olin is a Zen practitioner, so he might have that in mind, but I didn’t want to pin it down too closely. I love things that aren’t explained, and I don’t think you’ve got to write dystopian novels of science fiction; I find present-day, ordinary, day-to-day life infinitely strange.”

On a bitterly cold afternoon in January, the 86-year-old author sits soaking up the sun by the French doors to his patio, considering his 60-year career. He’s always viewed fiction as his true calling, “but I got kind of pigeonholed with The Snow Leopard; that book fixed me in nonfiction. Also, in that period [the 1960s and ’70s] I was writing a lot for the New Yorker; it serialized about eight of my books, so I didn’t have to write anything else—it supported me. I’m not sorry that I spent so much time writing about social justice and the environment, because I believe so passionately in both, but I think that my novels are out of the ordinary. I don’t mean the quality—they may be good or bad, but they aren’t your usual thing—I was always trying to break new ground. They were enterprising; I took chances.”

“I think my best book, certainly my most original one, was Far Tortuga”—a novel that is highly experimental in both writing style and typography. “That came out of the New Yorker too; I did a nonfiction piece for the magazine [about turtle fishing in the Caribbean], but I told William Shawn after I did the research, ‘You know, Mr. Shawn, I’m going to hold back the best material; I’m going to do a novel with it.’ He’d spent a fortune on the article, but he said, ‘Go ahead, Mr. Matthiessen, do what’s right for you.’ There’s an editor for you.”

“I’ve had a lot of good editors, and a couple are still very good friends, but Shawn was an editorial genius, because he was so pure: incorruptible and very stubborn. And then there was the monetary part,” Matthiessen adds with an appreciative chuckle. “You never knew quite what to expect when you got the check, but it was always bigger than you expected it to be.”

His editor for In Paradise is Riverhead’s editorial director, Becky Saletan, who, by happy coincidence, was an assistant to his Random House editor when Matthiessen published Killing Mister Watson, first in the trilogy of 1990s novels that eventually became Shadow Country. (For many years, Viking published his nonfiction, Random his fiction.) This dark meditation on environmental destruction, racism, and endemic violence in the Florida Everglades was always intended to be a single volume, says Matthiessen. “When I first presented it, it was about 1,500 pages, and Random House said, ‘We can’t do this,’ so I broke it into three parts. They were, in the main, very well received—especially the last volume, Bone by Bone—but I didn’t like the second one, Lost Man’s River. I thought it had the best material in it, but the trilogy was like a dachshund: its belly scraped the ground, while the two ends stood firm. I just couldn’t bear it going out like that, and I thought it would only take me a year or two to bring it under 1,000 pages: it took six or seven!”

The process was murderous. “Don DeLillo once said to me, ‘Cutting is cutting the good stuff; the rest is just editing.’ So the cutting hurt”—he makes a gesture as if slashing open his stomach. “I cut what I thought was some very good stuff, but I had to do it.”

It’s been widely reported that Matthiessen has said In Paradise “may be my last word.” However, he acknowledges, “there’s a lot of pressure on me to write a memoir. Becky, I think, would like me to do it, and my agent [Neil Olson] definitely would—he says we should have placed it right after I won the National Book Award for Shadow Country. I’m not particularly tempted; it seems to me a poor way to wrap up your career, by writing strictly about yourself. I love telling stories about myself, I’m a big ham, and if you tell them often enough, because you’re amusing your friends, or whatever, all the uncomfortable stuff gets pared away and you’re telling a doctored version of your life, even though you think you’re telling the truth. Also, when all your friends have died, you get to have the last word and give yourself the benefit of the doubt.”

Matthiessen would really rather write another novel, and he has an idea for one. “But of course you hesitate to embark on something, let alone place it with a publisher, if you don’t know whether you’re going to be able to finish it. I’ve got a respectable body of work, 30 books; perhaps that’s enough. On the other hand, when I wake up in the morning, go and get my coffee, and I haven’t got something on my desk to go to, it’s terrifying.”