They started Ballantine Books in 1952, publishing reprints as well as original works in paperback.

While Ian Ballantine, who died in 1995, was the better known of the publishing duo, Betty Ballantine, who was British, quietly devoted herself to the editorial side. She nurtured authors, edited manuscripts and helped promote certain genres — westerns, mysteries, romance novels and, perhaps most significant, science fiction and fantasy.

Her love for that genre, and her knowledge of it, helped put it on the map.

“She birthed the science fiction novel,” said Tad Wise, a nephew of Ms. Ballantine’s by marriage. With the help of Frederik Pohl, a science fiction writer, editor and agent, Mr. Wise said, “She sought out the pulp writers of science fiction who were writing for magazines and said she wanted them to write novels, and she would publish them.”

In doing so she helped a wave of science fiction and fantasy writers emerge. They included Joanna Russ, author of “The Female Man” (1975), a landmark novel of feminist science fiction, and Samuel R. Delany, whose “Dhalgren” (1975) was one of the best-selling science fiction novels of its time.

The Ballantines also published paperback fiction by Ray Bradbury, whose books include “The Martian Chronicles” and “Fahrenheit 451”; Arthur C. Clarke, who wrote “2001: A Space Odyssey”; and J.R.R. Tolkien, author of “The Hobbit” and the “Lord of the Rings” trilogy.

“Betty was succinct and to the point and had a steely eye and was a respected editor,” Irwyn Applebaum, the former president and publisher of the Bantam Dell Publishing Group, now part of Penguin Random House, said in a telephone interview.

“Most people who knew the Ballantines would say that much of the editorial vision and brilliance, from variety to quality, that Bantam and Ballantine were known for were due to Betty,” Mr. Applebaum said. “Ian was the proselytizer for their brand of books, but Betty was the identifier, the nurturer, the editor.”

Elizabeth Norah Jones was born on Sept. 25, 1919, in Faizabad, India, during British rule on the subcontinent. She was the youngest of four children of Norah and Hubert Arnold Jones.