Ms. Lee had always lived simply, despite her fame and mounting wealth, and long shared a modest brick home in Monroeville with her older sister, Alice, who died in 2014. Ms. Lee could be seen around town in sweatpants looking for bargains at a Dollar General Store, washing her clothes at a local Laundromat, drinking coffee at a McDonald’s or eating at David’s Catfish House, where her usual iced tea and a small plate of catfish would cost about $6.

Often miscast as reclusive, she was no hermit, but she was as ferociously private as she was famous, and shunned interviews.

She was thrust into the spotlight three years ago, when “Watchman” was released. Its publication sparked a debate about whether or not Ms. Lee had been pushed into publishing the novel, one that she had abandoned in the 1950s as an early effort at the story that would become “Mockingbird.”

At the release of “Watchman,” there were already questions about Ms. Lee’s vulnerability and her mental and physical condition. She had suffered a stroke in 2007, had severe vision and hearing problems and had moved into an assisted living facility. In 2013, in a copyright dispute that went to court, Ms. Lee’s lawyers said she had been taken advantage of and coerced into signing away her copyright because she was “an elderly woman with physical infirmities that made it difficult for her to read and see.”

The controversy surrounding “Watchman” divided Ms. Lee’s hometown, pitting some of her longtime friends and acquaintances, who doubted she had approved of the publication, against Ms. Lee’s lawyer, agent and publisher, generating the kind of public spectacle Ms. Lee abhorred. But an Alabama agency investigated whether Ms. Lee was a victim of elder abuse and financial fraud and determined that no abuse had occurred.

Some scholars and fans embraced “Watchman” as a long awaited sequel to Ms. Lee’s debut work, while others dismissed it as an inferior rough draft, one that was eventually polished and reshaped into a masterpiece. Many fans were shocked to discover that Atticus Finch, the crusading lawyer who fights for racial equality in “Mockingbird,” is depicted in “Watchman” as an aging racist and segregationist who clashes with his daughter, a grown-up Scout, over her support for civil rights.