Writing in the Dictionary of Literary Biography, Susan Walker described Sontag's career as "marked by a seriousness of pursuit and a relentless intelligence that analyzes modern culture on almost every possible level: artistic, philosophical, literary, political, and moral."
But she also was lampooned for the headiness of her writing. In a backhanded tribute to her influence in popular culture, the baseball catcher played by Kevin Costner in the 1988 film "Bull Durham" calls her handful of novels "self-indulgent, overrated crap."
Susan Sontag characterized her motivations simply: to "know everything," starting with literature.
Sontag's own motivations were simple, she said: to "know everything." She had a lusty devotion to reading that she likened to the pleasure others get from watching television. "So when I go to a Patti Smith concert, I enjoy, participate, appreciate and am tuned in better because I've read Nietzsche," she told Rolling Stone magazine. "The main reason I read is that I enjoy it."
Susan Rosenblatt was born Jan. 16, 1933, in New York, the older daughter of a traveling fur trader and an alcoholic teacher. She was raised in Tucson and Los Angeles and was largely left alone as a young girl, she later told an interviewer. Raised by a nanny in her parents' absences, she was 5 when her mother came back from China alone. Her father had died of tuberculosis, and her mother revealed the truth months later only after the girl pressed for details about his return. She took the surname Sontag from her stepfather.
Sontag described a girlhood bereft of playmates. Instead, she devoured Djuna Barnes, Shakespeare, Victor Hugo and Jack London. "I got through my childhood," she told the Paris Review, "in a delirium of literary exaltations."
She met Thomas Mann after reading the German author's 1924 novel "The Magic Mountain," set in a European sanitarium. On a second read, she spoke the words aloud and was so enthused about the book that she conspired with a friend to meet the author, then living in Los Angeles in exile during the Nazi era.
"He seemed to find it perfectly normal that two local high school students should know who Nietzsche and [composer Arnold] Schoenberg were," she wrote in a New Yorker account of the visit.
Her stepfather warned her that being so interested in books would make her uninteresting to men. "I just couldn't stop laughing," she once said. "I thought, 'Oh gosh, this guy's a perfect jerk.' "
Before graduating from the University of Chicago in 1951 with a bachelor's degree in philosophy, she married Philip Rieff, a sociologist 10 years her senior whom she would divorce in 1959. They had a son, David Rieff of New York, who survives, along with Sontag's sister.
After Chicago, Sontag received master's degrees in English and philosophy from Harvard University and did all but her dissertation for a doctorate in philosophy.
Her first book, "Freud: The Mind of the Moralist" (1959), was completed in collaboration with her husband. They agreed, however, to put only his name on the title page.
Still, she described this time as liberating. She was 26, divorced and ready to experience what she described as a delayed adolescence filled with dance lessons, discussions with politically motivated young people and a desire to make a literary mark.
She taught religion at Columbia University before completing her first novel, "The Benefactors" (1963), the study of a dreamy rogue named Hippolyte who soon cannot tell reality from his own imagination. It impressed reviewers, and she began cornering magazine editors, sometimes at cocktail parties, about publishing her work.
Her analysis, for the Nation magazine, of Jack Smith's erotically flamboyant film "Flaming Creatures" (1963) brought her attention as an enthusiastic filmwatcher but caustic observer of American morality, which she saw as preventing a full-blown appreciation of the film's "aesthetic vision."