In Jaffe's 10 novels her surest instincts have been commercial

Behind locked dormitory doors, Glacia the Fighter, Freelik the Frenetic and Pardieu the Holy Man huddle around their master. He speaks: "In the forbidden caves of the Jinnorak live a mutated people once human, now changed from generations in the foul depths to creatures unrecognizable." Of his by-now rapt disciples, the leader demands: "Shall you enter?"

To the thousands of college students addicted to the campus craze Dungeons and Dragons, this gobbledygook will sound like a good session of the game, led by an especially inventive "Dungeon Master." But in Rona Jaffe's latest novel, Mazes and Monsters (Delacorte, $13.95), the strange adventures of Glacia, Freelik and Pardieu are twists of the plot. Jaffe's characters are students who assume medieval roles and play a game called "Mazes and Monsters" to forget their adolescent problems. "Going on an imaginary quest to kill monsters together gives them a closeness, a bonding in a group," explains the author.

Jaffe's interest in D&D was first aroused by newspaper stories about 16-year-old James D. Egbert III, a troubled Michigan State sophomore whose 1979 disappearance was mistakenly attributed to playing the game in the steam tunnels of his university. (He was later found and last year committed suicide.) A modified version of the scenario unfolds in Jaffe's novel, which she wrote in a mere five months.

The 49-year-old author has always been commercially prescient. As a young Radcliffe graduate, she wrote The Best of Everything, a 1958 bestseller that heralded a new breed of New York career girl clawing and sleeping her way out of the steno pool. In nine subsequent novels, including the 1979 best-seller Class Reunion (a replay of Mary McCarthy's The Group, set at Radcliffe instead of Vassar), she has exposed the scheming, skepticism and emotional woes of contemporary women. "Show me a man who won't run away when a girl says I love you," Rona once declared, "and I'll show you a man who's married to someone else."

Jaffe herself has remained the resolutely single career woman who puts her work first. Even as a child in Brooklyn she was a determined poet, writing her first verse at age 2½. Rona's parents, a high school principal and his wife, urged her on. By the time Rona was 9, she was submitting short stories to The New Yorker. Once when a rejection notice arrived, she stormed over to the magazine's office to find out why.

After graduating from college in 1951, Jaffe worked for a publishing house while writing short stories. At the offices of her agent one day, she bumped into Warren Beatty, then a struggling young actor. "I was wearing a halter top and he bit my stomach," she recalls laughingly. "He used to call me up afterward and ask if he could come over and bite it again." Undiscouraged by this brush with show business, Jaffe enrolled in drama and playwriting classes at Lee Strasberg's Actors' Studio, where her fellow students included Paul Newman, Shelley Winters and Marilyn Monroe.

Over the years, Jaffe has kept in touch with her actor friends, and balances a life on the celebrity party circuit with intense periods of writing in her stylish one-bedroom Manhattan apartment. Fiercely private about the men in her life, she says, "I'm independent enough not to keep saying, 'Hey, I have a boyfriend, you know.' " A moderate feminist, Jaffe is grateful to the women's movement for "helping men understand that if you want to write books, you're entitled to." No longer, she says, "do you have to act like it's a little hobby that you do on the side."