Harper Lee was an ordinary woman as stunned as anybody by the extraordinary success of “To Kill a Mockingbird.”

“It was like being hit over the head and knocked cold,” Lee – who died Friday at age 89, according to publisher HarperCollins – said during a 1964 interview, at a time when she still talked to the media.

“I didn’t expect the book to sell in the first place. I was hoping for a quick and merciful death at the hands of reviewers, but at the same time, I sort of hoped that maybe someone would like it enough to give me encouragement.”

“To Kill a Mockingbird” may not be the Great American Novel. But it’s likely the most universally known work of fiction by an American author over the past 70 years, that rare volume to find a home both in classrooms and among voluntary readers, throughout the country and beyond.

Lee was cited for her subtle, graceful style and gift for explaining the world through a child’s eye, but the secret to the novel’s ongoing appeal was also in how many books this single book contained.

“To Kill a Mockingbird” was a coming-of-age story, a courtroom thriller, a Southern novel, a period piece, a drama about class, and – of course – a drama of race.

It was an instant and ongoing hit, published in 1960 as the Civil Rights movement was accelerating. It’s the story of a girl nicknamed Scout growing up in a Depression-era Southern town. A black man has been wrongly accused of raping a white woman, and Scout’s father, the resolute lawyer Atticus Finch, defends him despite threats and the scorn of many.

Praised by The New Yorker as “skilled, unpretentious, and totally ingenious,” the book won the Pulitzer Prize and was made into a memorable movie in 1962, with Gregory Peck winning an Oscar for his portrayal of Atticus.

“Mockingbird” inspired a generation of young lawyers and social workers, was assigned in high schools all over the country and was a popular choice for reading programs, although it was occasionally removed from shelves for its racial content and references to rape.

By 2015, sales topped 40 million copies. When the Library of Congress did a survey in 1991 on books that have affected people’s lives, “Mockingbird” was secondonly to the Bible.