Harper Lee, the Alabama-born novelist whose Pulitzer Prize-winning best-seller To Kill a Mockingbird has been a mainstay of American educational reading lists since its publication in 1960, died in her Monroeville home on Friday. She was 89.

By several accounts, Lee had been in failing health for some time, and while there were those who questioned her state of mind in her final years, Wayne Flynt, an Alabama author-historian and friend of Lee's for more than a decade, recently told The New York Times: "I don't think that anybody that says she's demented has been to see her in the last 10 years. The problem may be that almost nobody goes to see her, almost nobody gets in. She's such a private person."

Her death comes on the heels of the announcement in early February that July 14, 2015, would see the publication of Go Set a Watchman, the long-awaited second book by Lee. It "features the [Mockingbird tomboy heroine] character known as Scout as an adult woman," the author herself said in a statement released through her publisher.

Originally written in the 1950s, Watchman is effectively a follow-up to Lee's breakthrough debut novel, which in its 55 years has sold a remarkable 40 million copies.

So profound was the reaction to the new book's announcement that it not only made all the television newscasts and generated international Twitter comment, but it sent sales of her original work skyrocketing once again. Amazon.com in the U.K. alone reported an increase in sales of the novel To Kill a Mockingbird to be up 3,000 percent, and sales of the DVD of the 1962 film adaptation – which brought the Best Actor Oscar to its leading man, Gregory Peck – up 1,200 percent.

Though transparently autobiographical on the author's part, the novelist's fictional hero, Atticus Fitch, is the widowed father of two children, Jem and Scout, and a small-town lawyer in the Jim Crow South. Their very quiet lives are forever changed when Atticus takes on the case of a black man accused by a white girl of a sexual assault that he did not commit.

"Pleasant, undemanding reading," critiqued the Atlantic Monthly in its original review, though others were far less restrained. Time magazine outright lauded the work, saying, "Author Lee, 34, an Alabaman, has written her first novel with all of the tactile brilliance and none of the preciosity generally supposed to be standard swamp-warfare issue for Southern writers. The novel is an account of an awakening to good and evil . . . [Lee] teaches the reader an astonishing number of useful truths about little girls and about Southern life."

With that, an instant new literary celebrity was born – one who would then spend nearly the rest of her life avoiding the spotlight, avoiding interviews and, most especially, avoiding the publication of another book.

Truman Capote a Childhood Friend

Nelle Harper Lee was born on April 28, 1926, in Monroeville, Alabama, and she hated her first name, because people would pronounce it "Nellie." So she simply dropped it. Harper was the youngest of four children and an unabashed tomboy. Her lawyer father, Amasa Coleman Lee, served in the Alabama state legislature and was part owner of the town newspaper, while her reclusive mother, Frances Cunningham Finch) beset by mental illness, rarely left the house.

During their Monroeville childhoods, Lee developed a lifelong friendship with Truman Capote, a boy sent to live next door with his aunt and uncle. As an adult, Lee had plenty of reasons to be angry at the celebrated writer, such as his never properly acknowledging her substantial contributions helping with his 1966 masterwork In Cold Blood, or, earlier, his petty jealousy over her tremendous success with To Kill a Mockingbird. Still, these were things she would never acknowledge publicly.

In high school, Lee concentrated on English literature and graduated in 1944. She attended the all-female Huntingdon College in Montgomery, Alabama, where rather than participate in the campus social scene, she devoted time to studying and writing, as well as joining the literary honor society and the glee club.

Transferring to the University of Alabama at Tuscaloosa, she took up studying law, only to leave school, much to her father's disappointment. She further grieved him by up and moving to New York City, where she reconnected with Capote, worked as an airline ticket agent and found generous benefactors: the couple Joy and Michael Brown (he wrote for Broadway). In 1956, they gave her enough money to support her efforts at writing.

By 1957, Lee had a first draft of To Kill a Mockingbird, then worked with an editor for two more years on rewrites. When publication came, Lee struck gold, both critically and commercially – and after a few more years there was word that the author was at work on a second novel. Only it never came.

A Quiet Life

Instead, she assisted Capote on In Cold Blood – in the two screen biographies of Capote that were produced a decade ago, Lee was played by Catherine Keener in the film Capote (Truman was played by Philip Seymour Hoffman, in his Oscar-winning role) and by Sandra Bullock in Infamous (Toby Jones was Capote) – and slowly, but decidedly, withdrew from public life for something quiet, going to church and tending to herself in Monroeville. She spent her last years in an assisted-living facility.

And despite the ongoing high profile of her work, Lee never personally appeared to accept any of honorary doctorates and awards she received, and there were many – including the 2007 Presidential Medal of Freedom.

In bestowing that honor, then-President George W. Bush said, "Forty-six years after winning the Pulitzer Prize, To Kill a Mockingbird still touches and inspires every reader. We're moved by the story of a man falsely accused – with old prejudice massed against him, and an old sense of honor that rises to his defense. We learn that courage can be a solitary business. As the lawyer Atticus Finch tells his daughter, 'Before I can live with other folks I've got to live with myself. The one thing that doesn't abide by majority rule is a person's conscience.' "

Plainly, these were words that Harper Lee lived by.