Harper Lee, whose first novel, “To Kill a Mockingbird,” about racial injustice in a small Alabama town, sold more than 10 million copies and became one of the most beloved and most taught works of fiction ever written by an American, has died. She was 89.

Her death was confirmed by HarperCollins, her publisher.

The instant success of “To Kill a Mockingbird,” which was published in 1960 and won the Pulitzer Prize for fiction the next year, turned Lee into a literary celebrity, a role she found oppressive and never learned to accept. The enormous success of the film version of the novel, released in 1962 with Gregory Peck in the starring role of Atticus Finch, a small-town Southern lawyer who defends a black man falsely accused of raping a white woman, only added to Lee's fame and fanned expectations for her next novel.

For more than half a century, it failed to appear. Then, in 2015, long after the reading public had given up on seeing anything more from Lee, a sequel appeared under mysterious circumstances.

“I never expected any sort of success with `Mockingbird,”' Lee told a radio interviewer in 1964. “I was hoping for a quick and merciful death at the hands of the reviewers, but, at the same time I sort of hoped someone would like it well enough to give me encouragement.” Instead, she said, “I got rather a whole lot, and in some ways this was just about as frightening as the quick, merciful death I'd expected.”

Lee gained a reputation as a literary Garbo, a recluse whose public appearances to accept an award or an honorary degree counted as important news simply because of their rarity. On such occasions she did not speak, other than to say a brief thank you.

In Feb. 2015, her publisher, Harper, an imprint of HarperCollins, dropped a bombshell. It announced plans to publish a manuscript, long thought to be lost, that Lee submitted to her editors in 1957 under the title “Go Set a Watchman.” Lee's lawyer, Tonja B. Carter, had chanced upon it, attached to an original typescript of “To Kill a Mockingbird,” while looking through Lee's papers, the publishers explained. It told the story of Atticus and Scout 20 years later, when Scout is a young woman living in New York, and included several scenes in which Atticus expresses conservative views on race relations seemingly at odds with his liberal stance in the earlier novel.

The book was published in July with an initial printing of 2 million and, with enormous advance sales, immediately leapt to the top of the fiction best-seller lists, despite tepid reviews.

The book soared miles above such criticisms. By the late 1970s “To Kill a Mockingbird” had sold nearly 10 million copies, and in 1988 the National Council of Teachers of English reported that it was being taught in 74 percent of the nation's secondary schools. A decade later Library Journal declared it the best novel of the 20th century.

Nelle Harper Lee was born in the poky little town of Monroeville, in southern Alabama, the youngest of four children. “Nelle” was a backward spelling of her maternal grandmother's first name, and Lee dropped it when “To Kill a Mockingbird” was published, out of fear that readers would pronounce it Nellie, which she hated.

Her father, Asa Coleman Lee, was a prominent lawyer and the model for Atticus Finch, who shared his stilted diction and lofty sense of civic duty. Her mother, Frances Finch Lee, also known as Miss Fanny, was overweight and emotionally fragile. Truman Capote, a friend of Lee's from childhood, later said that Nelle's mother had tried to drown her in the bathtub on two occasions, an assertion that Lee indignantly denied.

Lee was a tough little tomboy who enjoyed beating up the local boys, climbing trees and rolling in the dirt. “A dress on the young Nelle would have been as out of place as a silk hat on a hog,” recalled Marie Rudisill, Capote's aunt, in her book “Truman Capote: The Story of His Bizarre and Exotic Boyhood by an Aunt Who Helped Raise Him.”

One boy on the receiving end of Nelle's thrashings was Truman Persons (later Capote), who spent several summers next door to Nelle with relatives. The two became fast friends, acting out adventures from “The Rover Boys” and, after Nelle's father gave the two children an old Underwood typewriter, making up their own stories to dictate to each other.

Capote later wrote Nelle into his first book, “Other Voices, Other Rooms,” where she appears as the tomboy Idabel Tompkins. She made a repeat appearance as Ann Finchburg, nicknamed Jumbo, in his story “The Thanksgiving Visitor.” Lee returned the favor, casting Capote in the role of the little blond tale-spinner Dill in “To Kill a Mockingbird.”

Lee attended Huntingdon College, a local Methodist school for women, where she contributed occasional articles to the campus newspaper and two fictional vignettes to the college's literary magazine. After a year at Huntingdon, Lee transferred to the University of Alabama to study law, primarily to please her father. Her own interests, and perhaps her disposition, led her elsewhere. After her senior year, she spent a summer at Oxford University as part of a student-exchange program. On her return from England, she decided to go to New York and become a writer.

Lee arrived in Manhattan in 1949 and settled into a cold-water apartment in the East 80s. After working briefly at a bookstore, she found work as a reservations agent, first for Eastern Airlines and later for BOAC. At night she wrote on a desk made from a door. The local colony of displaced Southerners regarded her askance. “We didn't think she was up to much,” recalled Louise Sims, the wife of the saxophonist Zoot Sims. “She said she was writing a book, and that was that.”

Editors at Lippincott told Lee that her manuscript read like a string of anecdotes, not a novel, but encouraged her to revise. Eventually they paid a small advance and assigned her to work with Tay Hohoff, an experienced editor with whom she developed a close working and personal relationship.

Signs of its success were visible almost immediately after it was published in July 1960. Both Book-of-the-Month Club and the Literary Guild made the novel one of their selections, and Reader's Digest selected it for publication in condensed form. A week after its publication, it jumped to the top of the best-seller lists; it remained there for 88 weeks.

In one of her last interviews, with a Chicago radio show in 1964, Lee talked in some detail about her literary ambition: to describe, in a series of novels, the world she grew up in and now saw disappearing. “This is small-town middle-class Southern life as opposed to the Gothic, as opposed to `Tobacco Road,' as opposed to plantation life,” she told her interviewer, adding that she was fascinated by the “rich social pattern” in such places. “I would simply like to put down all I know about this because I believe that there is something universal in this little world, something decent to be said for it, and something to lament in its passing,” she continued. “In other words, all I want to be is the Jane Austen of South Alabama.”

News of the rediscovery of “Go Set a Watchman” threw the literary world into turmoil. Many critics, as well as friends of Lee, found the timing and the rediscovery story suspicious, and openly questioned whether Lee, who was shielded from the press by Carter, was mentally competent to approve its publication. It remained an open question, for many critics, whether “Go Set a Watchman” was anything more than the initial draft of “To Kill a Mockingbird.”

In a statement, Lee, who said that she had assumed the manuscript was lost, wrote, “After much thought and hesitation, I shared it with a handful of people I trust and was pleased to hear that they considered it worthy of publication.”