IN AN ERA WHEN EXHIBITIONISM IS regarded as cathartic—when chat-show guests share their sexual fantasies and America knows that its President wears boxer shorts—Caroline Kennedy might have been forgiven for serving up the occasional intimate anecdote. As coauthor with Ellen Alderman of The Right to Privacy, an examination of an issue that is remarkably close to the bone, she could easily have drawn upon scenes from her own life—being ambushed by photographers, for example, as she strolled in Central Park with Jacqueline Kennedy Onassis just days before her death.

But for Kennedy, 37, intrusions on public figures are beside the point. She and Alderman, 37, a classmate at the Columbia University School of Law and coauthor of their 1991 best-seller, In Our Defense: The Bill of Rights in Action, are interested in trespasses against the privacy, dignity and bodily integrity of ordinary folk—"people," says Kennedy, "who are completely private and suddenly something about their life is very public." A case they found particularly chilling involved a Chicago woman arrested in 1978 for driving the wrong way down a one-way street; hauled to the city jail, where many traffic offenders were then taken, she endured a rough strip-search. (She later sued the city and ultimately won $75,000.) "Most of us have made a wrong turn," says Kennedy, "and it could have been you."

Convinced, in Kennedy's words, that "the law is really about people," the two found inspiration for the new book while promoting Bill of Rights. "People asked a lot of questions related to privacy," says Alderman (who lives in Yarmouth, Mass., with husband Bill Harwood, 43, a lawyer, their daughter, Kate, 1, and Harwood's three other children, who live with them part-time). Intrigued, the authors plunged into Privacy in 1992. They scoured law journals for essays on privacy, debriefed attorneys and spent hours online, searching for compelling cases.

Together, they tracked down and interviewed both plaintiffs and defendants—most of whom were eager "to say their piece on something enormous in their lives," says Kennedy. The authors' subjects included publisher Larry Flynt, who lost a 1982 suit brought by an animal trainer mortified when her photo with her diving pig was published in a satirical column in his seamy Chic. The two spoke with Flynt in his Beverly Hills office—an enclave enlivened by statues of copulating nudes. "You wouldn't mistake [it] for someone else's," as Kennedy has put it.

When Alderman and Kennedy began writing in 1992, they divided the material equally, each editing the chapters written by the other. "I would be so happy when I was ready to hand over to Ellen, because it would come back a lot better," Kennedy says.

The book (which, according to Knopf, is selling briskly), "is a unique achievement," states Kathleen M. Sullivan, professor of law at Stanford Law School. "In law school we tend to treat people as incidental. In this book people are central."

Low-key and unassuming, Kennedy is skilled at protecting her own privacy. She refuses to discuss the intrusions of the press into her own life, although she acknowledges, "Obviously, it's something I grew up thinking about." Interviews are held at her publisher's office, never in the Park Avenue co-op she shares with her husband of nine years, Edward Schlossberg, 50, and their children, Rose, 7, Tatiana, 5, and John, 2. Accustomed to taking the subway, she wears a poor-boy sweater and dark trousers for a meeting with a reporter; when a secretary mistakenly brings her coffee without cream, she drinks it black rather than risk seeming a prima donna. "She's astonishingly well-adjusted to her fame," says Peter Gethers, who edited The Right to Privacy.

In Alderman, Kennedy has an ideal, and equal, partner, he says: "Let's face it—Caroline is the star. But they're a good team. Ellen is a little protective of her because of who she is, and Caroline's protective of Ellen—she doesn't want to be seen as the driving force."

Since Alderman met Kennedy in 1986, the two have coped with the demands of school, careers and hectic personal lives without ever losing the thread of their relationship. In the summer, they gather en famille on Long Island, where they have beach houses; at other times, the couples meet for dinner in Manhattan.

As Harwood notes, both faced "plenty of distractions" while the book was aborning. Kennedy's son John was born in January 1993; later that year Alderman married. In 1994, Alderman's daughter arrived, and, of course, Kennedy's mother died. "It was hard to concentrate," she admits. "When I was able to get back into the book, knowing she was interested in [it] helped me. And having a partner made a huge difference—if one of us isn't working, the other usually is."

After a 10-city tour, the two plan to concentrate on their private lives. Each will have more time to spend with her children—something that was at a premium during the book's final drafting. "This is a fun time of year," Kennedy says. During the holidays, "I look forward to just being home."

JENNIFER FREY in New York City