Nora Johnson (Judy Feiffer/Simon & Schuster)

Nora Johnson, who portrayed the breathless infatuation of two schoolgirls with a concert pianist in her novel, “The World of Henry Orient,” which she helped adapt into a popular movie starring Peter Sellers, died Oct. 5 at an assisted-living center in Dallas. She was 84.

A daughter, Marion Siwek, confirmed the death but did not specify the cause.

Ms. Johnson published seven novels and several other books, including memoirs about her father, Hollywood screenwriter, producer and director Nunnally Johnson. But she was best known for “Henry Orient,” which was derived from her teenage crush on the pianist, actor and wit Oscar Levant.

Ms. Johnson published the novel in 1958, when she was 25, and was praised by critic Judith Crist in the New York Herald Tribune for having “a very special gift for recalling — and recreating — the poignant bittersweet of late childhood.”

In the book, two students at a private girls’ school in New York become obsessed with Orient, tracking his every move around the city.

Author Nora Johnson with her father, screenwriter and producer Nunnally Johnson. (Family Photo)

Unusual for the time, both girls are the children of divorce, and one of them leaves school early each day for psychoanalysis.

Nevertheless, Ms. Johnson captured the girls’ lives with a spirit of exuberance, showing them practicing the piano, writing in journals, trying on adult clothing and manners, and recording every sighting of Henry Orient in their notebooks. Their relentless spying reveals some unsavory facts about their hero and people closer to home.

Ms. Johnson and her father adapted “The World of Henry Orient” for the screen, with Sellers in the title role. The two schoolgirls, Valerie Boyd and Marian Gilbert, were played by Tippy Walker and Merrie Spaeth, respectively.

The 1964 film, directed by George Roy Hill, which is considered something of a visual love letter to Manhattan, became a cult favorite and is often shown on classic movie channels.

New York Times critic Bosley Crowther called it “one of the most joyous and comforting movies about teenagers that we’ve had in a long time” and praised Sellers’s “ever-surprising” portrayal of Orient as “a poseur, a popinjay, a fraud — an arch deceiver of women.”

Ms. Johnson never equaled the success of “Henry Orient,” but several of her other novels were well received. In her memoirs, she wrote about her divided life as a child, spent partly in New York with her mother and partly in Los Angeles with her charismatic father — “almost a legend in Hollywood” — where she was surrounded by “an encampment of storytellers.”

As a girl, she saw Judy Garland, Humphrey Bogart, Lauren Bacall and Marilyn Monroe at her father’s glittering parties. Tyrone Power and Darryl F. Zanuck played croquet on the lawn, and songwriter Johnny Mercer crooned “One for My Baby” at the piano.

“The high points in my young life were being alone with Nunnally,” Ms. Johnson wrote in a 2004 memoir, “Coast to Coast: A Family Romance,” “being gently courted, taken out on the town, admired and listened to with no distractions, being introduced to glamorous people, being treated like a remarkable female person.”

Nora Johnson was born Jan. 31, 1933, in Hollywood. Her parents met while they were reporters for the Brooklyn Eagle newspaper.

Her father was the screenwriter and producer of dozens of films, including “The Grapes of Wrath” (1940) and “How to Marry a Millionaire” (1953), and also wrote and directed “The Man in the Gray Flannel Suit” (1956) and “The Three Faces of Eve” (1957).

She was 6 when her parents divorced. She moved to New York with her mother, the former Marion Byrnes, and attended the private Brearley School, the inspiration for the school in “Henry Orient.” She graduated in 1954 from Smith College in Northampton, Mass., where she was in classes with poet Sylvia Plath.

Ms. Johnson lived most of her life in New York before moving to Dallas less than two years ago.

Her marriages to Leonard Siwek and Jack Milici ended in divorce. Her third husband, George Johnston, died in 2011. Survivors include two daughters from her first marriage, Marion Siwek of Los Angeles and Paula Siwek of Durham, N.C.; a son from her second marriage, Justin Milici of Dallas; two half-brothers; two half-sisters; and nine grandchildren. A son from her second marriage, Jonathan Milici, died in 2001.

Ms. Johnson’s other books included the novels “A Step Beyond Innocence” and “Tender Offer,” as well as “Flashback,” about her father and the memoir “You Can Go Home Again.”

In 1967, Nunnally Johnson adapted “The World of Henry Orient” for a stage musical, causing a short-lived rift with his daughter, who opposed the idea. The play closed on Broadway after 80 performances.

Nevertheless, her father remained a lasting influence throughout her life.

“It was inevitable that I should become a writer,” Ms. Johnson said in 1986. “Even now when I write a passage that pleases me especially, I find myself thinking, ‘How he’d like this . . . I hope.’ ”