[Below, Elsen relates O'Brien's personal reasons for writing fiction about the Vietnam War, specifically In the Lake of the Woods.]

Like the protagonist of his new novel, In the Lake of the Woods, Tim O'Brien has been driven to do what be considers terrible things because of his need for love.

For Mr. O'Brien, the commission of sin began in earnest in 1969, when he decided to go to Vietnam instead of to Canada after he was drafted into the Army, he said in a recent telephone interview from his home in Cambridge, Mass. He believed the war was wrong—he had even protested it—but he served anyway. "I went to the war purely to be loved, not to be rejected by my hometown and family and friends, not to be thought of as a coward and a sissy," he explained.

Once in Vietnam, he committed what he considers to be sins to gain the love and respect of his comrades. "If friends are burning houches, you don't want to be thought of as a bad person, so you burn along," he said. "You'll do bad things to be loved by your friends, realizing later you've made a horrible mistake."

A year after the My Lai massacre, which he recounts in In the Lake of the Woods, Mr. O'Brien was stationed in the village. He understands the fury felt by the soldiers who did the killing, though he says their actions can never be justified. "There's a fine line between rage and homicide that we didn't cross in our unit, thank God," he said. "But there's a line in the book about the boil in your blood that precedes butchery, and I know that feeling."

When he returned home, he said, he compounded his sins by keeping them secret, fearing that otherwise he would lose people he loved. "The deceits I write about in the book are magnified versions of the secrecy and deceit I practice in my own life, and we all do. We're all embarrassed and ashamed of our evil deeds and try to keep them inside, and when they come out, the consequences are devastating." He added that he wanted to "write a book where craving for love can make us do really horrid things that require lifelong acts of atonement. That's why I write about Vietnam. It was given to me, and I'm giving it back."

Now he plans to make some changes. Writing In the Lake of the Woods, which took him six years, was a start. He said he decided to put a mystery at the heart of the story and to break away from a straight narrative (though he feared that critics would object) because that is how the novel worked naturally. "This book is a way of helping myself to start to say, 'No, I'm not going to do things I think are wrong and stupid so people will like me.'"

He also plans to stop writing fiction for the foreseeable future. "The object of writing is to make a good piece of art," he said. "As you're making that art, you're tussling with the wicked self inside. That can get depressing, when you tussle with it for six years."

For now, he aims to stick with writing essays, working out, quitting smoking and improving his golf game. "I feel like I've gone to the bottom of a well with this book," he said.