"A River Runs Through It" is a semi-autobiographical account of Maclean's relationship with his brother Paul and their upbringing in an early 20th-century Montana family in which "there was no clear line between religion and fly fishing." In a 1981 profile of Maclean, Esquire magazine described it as:
It is a story about Maclean and his brother, Paul, who was beaten to death with a gun butt in 1942. It is about not understanding what you love, about not being able to help. It is the truest story I ever read; it might be the best written. And to this day it won’t leave me alone.
I thought for a while it was the writing that kept bringing it around. That’s the way it comes back to me: I hear the sound of the words, then I see them happen. I spent four hours one afternoon picking out three paragraphs to drop into a column I was writing about the book, and in the end they didn’t translate, because except for the first sentence—“In our family, there was no clear line between religion and fly-fishing”—there isn’t anything in it that doesn’t depend on what comes before it for its meaning.
The novel is noted for using detailed descriptions of fishing and nature to engage with a number of profound metaphysical questions. In a review for the Chicago Tribune, critic Alfred Kazin stated: "There are passages here of physical rapture in the presence of unsullied primitive America that are as beautiful as anything in Thoreau and Hemingway".