Marriage features two protagonists: Marjorie Pope, the oldest daughter of a carriage manufacturer whose business has been ruined by the advent of the automobile, and R.A.G.

The novel traces the history of their relationship, which begins when an early airplane Trafford is piloting crashes into the garden of a house Marjorie's family is renting for the summer.

Trafford intends to devote himself to writing a book entitled From Realism to Reality, which is to be "a pragmatist essay, a sustained attempt to undermine the confidence of all that scholasticism and logic chopping which still lingers like the sequelae of a disease in our University philosophy," while Marjorie intends to devote herself to being "his squaw and body-servant first of all, and then—a mother.

But the novel preaches no particular political ideology, and its dénouement finds Trafford embracing and Marjorie accepting a diagnosis according to which humanity's fundamental problem is "the new, astonishing riddle of excessive power"[2] and a religious philosophy according to which "Salvation's a collective thing and a mystical thing—or there isn't any.

John M. Siddall of the American Magazine inquired about making a film version of the novel in 1919, and the rights to it were sold to Goldwyn Pictures in the early 1920s.