Looked at from both sides of the existential spectrum, Jacqueline Mitchard's life is either charmed or full of booby traps waiting to happen. Two years ago she was writing a "perfectly nice" novel when she read about a court case in a town near Madison, Wis., where she lives. In the case, the judge held that adopted, unrelated siblings who are not "blood relatives" have no legal rights to adopt a child orphaned when one of the siblings later dies. The case began to obsess Mitchard, who at the time was the mother of five children (some biological, some adopted with her first, now deceased husband), and was in the process of adopting a little girl, Mia, with her second husband.

After Mitchard told her agent, Jane Gelfman, "I can't stop thinking about what those people must be going through and what kind of stakes they're facing," Gelfman encouraged Mitchard to put aside her novel in progress and write from her obsession. Then, a third of the way through the book, which chronicles the battle of two families for the custody of a toddler, Mitchard and her husband found themselves involved in a suit brought by Mia's father, who challenged their application for adoption. Thrust into the heartwrenching dilemma she was portraying in fiction, Mitchard finished her third novel, A Theory of Relativity, to be released by HarperCollins on June 19.

Mitchard has certainly weathered a rollercoaster of publishing experiences. After the huge success of The Deep End of the Ocean (Viking), which gained stellar honors as the first selection of Oprah's Book Club in 1996, she rushed to finish her second novel. "There was much urgency about seeing if my name would give this book great bounce," Mitchard explained. "I felt not only second-novel anxiety but also the residue of the Oprafication experience." When The Most Wanted (also Viking) met with mixed reviews and middling sales Mitchard understandably felt jittery about facing the world with her next effort. All the more reason, then, to convey the thorny legal problems with great accuracy, which called for extensive research.

Mitchard said she was relieved when Patti Kelly, then director of publicity at Viking, mentioned she was thinking of taking a year off. She immediately suggested that Kelly come to Wisconsin as her research assistant. "I don't know that I would have had the guts to take time off without Jackie's offer," Kelly told PW. "The experience was also a chance after many years on the other side to see what an author actually does."

Transmuting the original blood relative case into fiction proved more difficult because of Mitchard's own situation and also more complex in ways that enhanced the novel. For one thing, she started the book determined to understand, and then to convey, how the judge in the case could have decided to take the real-life toddler away from the family that had essentially raised her. It was a challenge, she said, to portray the judge as deeply caring, yet bound to evaluate the competing petitions from a legal standpoint. To fairly depict both families involved, and to indicate the protracted nature of the case, was "a matter of great delicacy," said Mitchard. She was anxious to convey the effects on the welfare of a child who becomes acclimated to one family but is claimed by others.

What was happening in Mitchard's personal life therefore seemed brutally ironic. "When I wrote The Deep End of the Ocean I felt I was building a wall of immunity around myself," Mitchard said. "I thought that if I wrote about something like kidnapping it wouldn't happen to me. I felt the same way about the custody battle that inspired A Theory of Relativity; if I wrote about it, I would be safe from something similar." Then Mia's father, who had been unaware of his daughter's birth, sued for custody, and Mitchard and her husband had to face the prospect of giving up a child they had grown to love. The experience, she said, deepened her understanding of "why there are no good guys or bad guys in this kind of custody battle. Mia's father was not a bad person when he challenged us. He was acting out of his own understanding of what kinship was. We went into an eight-month struggle in which we had to muster the gumption to fight someone who we had every reason to be grateful to. He was, after all, the father of our little angel." The case was resolved out of court, and Mitchard and her husband adopted Mia the day the actual jury trial would have begun. "Her father realized that she was now our child of the heart, and he couldn't bear to take her from us," she said.

It was not the first time Mitchard had seen her fiction turn true to life. She had created a character in The Most Wanted who was her own wish fulfillment. Widowed for five years, with five children under 12, she had visualized the character of Charley Wilder who shows up at her character Annie Singer's home to do some carpentry and stays on to marry her. When Christopher Brent Sornberger arrived on her doorstep to install ornamental tile a week after The Most Wanted was printed, Mitchard thought her character had come to life. "I had given up dating," she said, "because I knew my only hope of couplehood lay in someone younger than I, someone who would like the idea of raising a large family. So I made up my dream lover and decided he had to be in his 30s, and he had to able to fix things. He had to have a tool belt, and yet the soul of a poet." Struck by the similarities between Chris and his fictional counterpart, it didn't take Mitchard long to blurt out, " 'I think you're a character in my novel.' He said that no one had tried that line on him before." Theirs was a very short courtship, two months, "but I knew him," Mitchard said. "After all, I had made him up." That was three years ago.

In Mitchard's philosophy of life, all things turn out for the best. She decided to leave Viking after Barbara Grossman lost her job as publisher. "To me, Barbara was the heart and soul of the Viking that I loved." Grossman is among those thanked in the acknowledgments to A Theory of Relativity, for which she was an early reader. "She still steers and guides me. She always tells me the truth," Mitchard said. A factor in her decision to go to Harper was that Cathy Hemming—formerly of Viking and Random House—had relocated there as president and publisher. And in another coincidence, on her return to New York, Harper offered Patti Kelly a job as senior director of publicity. Meanwhile, Mitchard is pleased that the precedent-setting court case ruling against the adoptive sibling resulted in a groundswell of public opinion pressing for the reversal of the blood relative concept. In Wisconsin, the law has been changed to describe a relative "through birth or adoption." But she stressed that she doesn't want her book read as a message about the perils of adoption.

"This is not a book about adoption—or even about a custody case," she said. "It's really a book about people who are trying to do the right thing. It's more of a story about two families at a war they didn't choose. "

An appearance on the Today show on June 25th will inaugurate a 13-city book-signing tour. Then she'll go back to the book she's writing now, her "middle aged book," as she calls it. "This time I've given myself permission to be funny," Mitchard said. "It's Bridget Jones turns 45." Since the author herself became a grandmother in April, it's interesting to speculate if another toddler will make an appearance in this one, considering Mitchard's record of transforming life into art.