Leif Enger began writing when he was in the third grade. He would write small stories and poems mainly about baseball players and cowboys, but also at times about dinosaurs, gorillas, and his classmates. Enger has several ideals he follows when writing. The first of these is his belief that a character is best developed through action. A story should be "full of incident, not dialogue." Enger also believes in taking special care in "crafting" a story, and incorporating things that have meaning to you in what you write. Peace Like a River alone took him five years to write, and includes many parallels to his own life. For example: Enger's oldest son, just like his character Reuben in the story, suffers from asthma, and has had to learn to cope with this interference in his life. Writing the book was a slow process, and required patience from Enger's wife and children. Enger would read each and every scene to his family as he wrote it. His wife would advise him on his characters, while his sons helped him improve the story itself. In writing a novel, Enger never plans any themes ahead of time, he simply writes the story that he sets out to write. There is a major theme of loss in the novel. Lifestyles and family members are lost. There is also a major theme of miracles, both obvious and not. Did Enger have these themes in mind as he began writing his story? Not exactly. He always knew he wanted to write a story about a boy with a father that he believes can do extraordinary things. He also knew he wanted an outlaw brother on the run, and eventually, the death of a family member. But Enger didn't attempt to plan his story in a way that would express these themes, he just wanted to make sure his ideas were represented, and the themes would show themselves on their own.

Though it is not thought of primarly as a Western novel, Peace Like a River was intended to have a strong Western feeling. Even though the family never really makes it to Montana, the Western state they are headed for, there are plenty of Western characteristics in the story. Reuben's outlaw brother Davy is the most obvious, and so is Swede's obsession with the West. But Enger had a different reason for giving such a Western feel to his story. He believes that the West carries a feeling of "glory and obscurity". It's romantic and unforgiving, a perfect "testing ground" for a novel of the sort he set out to write. Enger knew that just like a set in a stage play, the west would provide him with a perfect place to allow his characters and his story to thrive.

Leif Enger has many influences in his writing style and idea of what a story should be like. His major influence is Robert Taylor, who published a "wonderful novel" in the late 1950s called The Travels of Jaimie McPheeters, about a young man heading west in the 1840s with his father, which one the Pulitzer Prize. The main character in the story, Jaimie, had an enormous influence on Reuben in Peace Like a River. Robert Louis Stevenson (who wrote such classics as Treasure Island and Kidnapped), was especially interesting to Enger because of the "flawed heroes and complicated villains" that he wrote. Other literary masters that influenced Enger included Jack London, Mark Twain, Charles Dickens, Flannery O'Conner, C.S. Lewis, Jim Harrison, Anne Tyler, Tom McGuane, Michael Chabon, Larry McMurty, and David Mamet. He is also influenced by religious figures such as Kind David, Solomon and the Apostle Paul. Enger is not only influenced by famous literary and religious figures, however. He also finds inspiration in his two sons. By trying to look at things through the perspective of his children, Enger was able to more accurately descrive how a person Reuben's age would react to what he experiences. Enger says that "Inspiration is everyplace."