The Age of Innocence is striking for its accurate and detailed description of upper-class life in New York City in the 1870s. The author -- who was a member of this society -- takes care to describe the carefully orchestrated customs and mores of that set the boundaries around and dictated the daily rituals of New York City's "leading families."
As a member of the high-society which she criticized in The House of Mirth, Edith Wharton was witnessing dramatic changes to that world, which was changed dramatically by the end of World War I. The tension between the 'old way' and encroaching 'new way' is drawn out in the character sketches of the leading characters. New Archer, the elgible bachelor, is betrothed to May Welland who is a product of the old traditions and ways. But he finds himself increasing drawn to the exotic Countess Ellen Olenska who has a more modern approach to the world and is willing to flaunt the old traditions.
The novel has been adapted into a film of the same name, The Age of Innocence.