NEW YORK – Susan Sontag, author, essayist, activist and intimidating public intellectual, died Tuesday at Memorial Sloan-Kettering Cancer Center. She was 71 and had suffered from leukemia.

Sontag had a long reign as the most intelligent woman in America, starting as a young critic writing for The Nation, Partisan Review, Harper’s and The New York Review of Books.

A strong-featured beauty with a trademark streak of white shot through her unruly black hair, Sontag became an intellectual celebrity in 1964 after publishing the essay “Notes on Camp,” in which she argued that style trumps substance and introduced the concept of “so bad, it’s good.”

After surviving a near-fatal bout of breast cancer in the early ’70s, she became even better known with “On Photography” and “Illness as Metaphor.”

In the first, Sontag examined how photographs have changed the way we see the world and ourselves. In the second, she explored the cultural myths we attach to certain illnesses.

In a 1992 interview, she revealed her ardor amid 15,000 books in her Chelsea apartment. “I’m an addicted reader,” she said as she laughed, “a hedonist. I’m led by my passions. It’s a kind of greed in a way.”

Born Susan Rosenblatt in New York in 1933, she was the daughter of an alcoholic mother and a father who died when she was 5 as he traded furs in China. Raised in Arizona and Los Angeles, Sontag left home at 15 after graduating from high school.

At 17, she married social psychologist Philip Rieff. They had a son, David, in 1952, but later divorced. Famed photographer Annie Leibovitz had been her longtime companion.

The author of 17 books, Sontag won the National Book Award in 2000 for a historical novel, “In America,” though she was criticized for the use of others’ research.

An unrelenting campaigner for human rights, Sontag served as president of the American chapter of PEN, the international writers organization dedicated to freedom of expression, from 1987 to 1989.

After Sept. 11, she took the lead among intellectuals arguing that U.S. foreign policy led to the attacks.

“Whatever may be said of the perpetrators of Tuesday’s slaughter, they were not cowards,” she wrote in the New Yorker. Once again she was at the center of a storm – hallowed ground for Sontag.