Set in the early decades of the 20th century among Finnish immigrants in Washington State, Karl Marlantes’s second novel seems a drastic shift from Matterhorn, his acclaimed 2010 debut based on his experiences as a Marine in Vietnam. Yet Deep River, which Atlantic Monthly Press will publish in July, was also sparked by a personal link: “I grew up in a little town on the Oregon coast where everybody was connected to the logging industry,” the writer says. “That’s in my background, and I always wanted to write about it.”

Marlantes’s mother’s family was Finnish, and he says that he grafted his grandmother’s political convictions onto Aino, one of Deep River’s protagonists. “Grandma was a communist; the Daily Worker was always in the house, that was normal to me. She had also been involved with the IWW, the Industrial Workers of the World. When I was just out of college, I heard this wonderful song Joan Baez sang about Joe Hill.” He sings a few lines of the labor anthem paying tribute to Hill, an IWW organizer who was executed by firing squad and considered a martyr by many in the movement. “I asked Grandma, ‘Did you know Joe Hill?’ and she said, ‘That son of a bitch!’ She said people down the ranks would spend years organizing, trying to get workers to hold the IWW red card, and then Hill would show up for one night, cops all over the place, and people would tear up their cards because they were afraid. He was a romantic figure to some, but to her he was a disturbing figure. I thought that was an interesting historical angle.”

Speaking via Skype from his home in the foothills of the Cascade Mountains, Marlantes sits outside on a lovely spring day, swinging his laptop around to show me his dogs and a grassy landscape stretching down to a pond, where he points out mallards landing on the water. It’s a gentle, idyllic setting, unlike Matterhorn’s war-blasted terrain and the mighty old-growth forests within which his characters love and labor in Deep River.

“I’m always struck by the heroism of those early settlers,” Marlantes says. “Those trees were huge; it sometimes took more than a day to cut one down. These people were brave, but the result was that they cut it all down; the old-growth forest is gone except for a few national parks. I’m struck by the irony of it: my grandmother and her brothers and friends—their view was that to get rid of this forest and put farms there; that was good.”

For all the gritty realism of scenes showing loggers at work and Aino agitating for “one big union,” Deep River has a mystical undercurrent most evident in the passages involving Vasutäti, a Native American woman who imparts shamanistic wisdom to Aino’s brother Ilmari. Marlantes’s principal characters align fairly closely with mythic figures in The Kalevala, a collection of ancient poems that form the bedrock of Finland’s cultural heritage. The writer used a similar strategy in Matterhorn, which drew on the medieval legend of Parzival.

“I’ve been interested in mythology since I was a child,” Marlantes says. “When I was in eighth grade, a local librarian put me onto The Celtic Twilight by Yeats. I was fascinated by these fairy stories he had collected, and then I got into Jung, and then Joseph Campbell. I began to see that the great mythologies have symbolism that means so much to our development as a culture and as individuals. The reason that they’re still with us is that they’re still meaningful: Parzival is the story of the development of a young man into manhood; “Amor and Psyche” is the myth of the development of a young woman into womanhood—bits of that got into Aino’s story. My feeling is that because these symbols have stayed with us for thousands of years, they ought to be damn good in a book. I think they work on the reader. People can read the novel without knowing anything about the myths, but these symbols are going to reach into some part of the psyche that needs to be reached. It’s soul talk.”

Weaving this kind of a dense narrative makes for long novels; Matterhorn and Deep River both weigh in at more than 600 pages. “The initial draft of Deep River was 350,000 words,” Marlantes remembers. “It’s not as big as Anna Karenina, which is 351,000 words, but it’s long. I sent it in, and I didn’t hear anything for ages from Morgan [Entrekin, president and publisher of Grove Atlantic]. Finally, after about two and a half months, I got a six-word email: ‘Great stuff. Too much of it.’ ”

Marlantes laughs. “I told Morgan, ‘It’s not as big as Anna Karenina,’ and he said, ‘Karl, I could never sell Anna Karenina today!’ I cut about 150,000 words, including whole characters; I had another brother and his wife in there—I hated to see them go, they were wonderful characters, but Morgan was right.”

Marlantes says he has to write long. “Once I get going and it’s flowing, I’m not going to stop it. I write by hand, and when it’s going well, I have the feeling that I’m not really there; I’m out of the way. I get into that world, and I actually wake up surprised that I’m in my office and it’s the 21st century. I edit later; 90% of the work is editing. It’s always a hard choice, but that’s the way I write.”

Marlantes has already “pretty much thought through” his next novel, though he hasn’t yet written the outline, typically a crucial first step for him. Its hero is the son of one of the brothers in Deep River. “He goes to West Point and becomes a career officer, and because he speaks Finnish, he becomes a military attaché to Finland in 1947,” Marlantes says. “He gets drunk one night at an embassy party and hits it off with a Russian officer, even though it’s the beginning of the Cold War, because they’re both military guys. They challenge each other to a ski race from the Arctic Circle to Helsinki, but the novel is not about the ski race; its point of view is these two men’s wives.”

“The American wife is a cheerleader with a typical American view of the world,” Marlantes explains. “She starts to brag about how good her husband is at skiing and about how there’s this race going on, which neither of the men intended to be public. The Finnish newspapers pick it up, then the London and New York papers, and suddenly it’s become a big deal: the American vs. the Russian. The Russian wife realizes that if her husband loses—this is the age of Stalin and Beria—at best, they’ll end up in Siberia. The cheerleader has to learn that there’s a lot more at stake than winning and losing. I’m thinking about calling it The Winner. Hopefully it won’t be 350,000 words!”