Harper Lee, author of To Kill a Mockingbird, one of the most treasured—and controversial—books in the American literary canon, died on Friday of natural causes at an assisted living facility in her hometown of Monroeville, Alabama. She was 89. Lee published To Kill a Mockingbird in 1960 and it went on to become an American classic, earning Lee the Pulitzer Prize for fiction in 1961, and a lasting place on required reading lists at schools across the country. Its controversial plot, which revolves around Alabama attorney Atticus Finch (father of Scout and Jem) defending an African-American man accused of raping a white woman, also landed it on banned book lists. To Kill a Mockingbird is widely believed to be at least loosely based on Lee’s own upbringing in Alabama, where her father, defended two black men accused of murder in 1919. (He lost the case, and the men were hanged.) (Scout’s childhood friend Dill is thought to be based on Lee’s lifelong friend, author Truman Capote.) By 1962, the book had been adapted into an Oscar-winning film starring Gregory Peck as Atticus Finch. Though Lee was considered a heroine of the Southern Gothic movement, she shunned literary stardom, and seldom made public appearances in the decades following. She didn’t publish another book until last year’s Go Set a Watchman, an early draft of To Kill a Mockingbird written in the mid-1950s and allegedly found by Lee’s attorneys in a safe-deposit box in 2011. It raised questions about whether Lee—age 88 and residing at the Meadows, an assisted living facility—was well enough to agree to the publication of the manuscript. She had long vowed she’d never publish another book, but an investigation by the state of Alabama found no evidence of elder abuse or coercion. Lee’s greatest work is as relevant today as it was almost 60 years ago. “You never really understand a person until you consider things from his point of view,” she wrote in To Kill a Mockingbird. “Until you climb inside of his skin and walk around in it.”