Somewhere between the repressiveness of Edith Wharton’s early-20th-century “Age of Innocence” and our own libertine “Shades of Grey” era lies the absorbingly sensuous world of Jennie Fields’s “The Age of Desire,” her reimagining of the midlife relationship between Wharton and journalist Morton Fullerton.

In the tradition of novels like Nancy Horan’s “Loving Frank,” about Mamah Borthwick’s affair with Frank Lloyd Wright, Fields employs characters and situations drawn closely from life. Her Wharton is rich, gifted, and unhappy, though already a literary sensation (for “The House of Mirth”) when we meet her in 1907 at a Paris salon. Fields’s third-person narration alternates between Wharton’s point of view and that of her loyal and perceptive governess-turned-secretary, Anna Bahlmann.