Though she’s been publishing fiction since 1987, Philippa Gregory is best known for the series of 15 historical novels she introduced in 2001 chronicling the lives of key women—Anne Boleyn, Katherine of Aragon, and Jane Grey among them—in Britain’s Plantagenet and Tudor courts. With Tidelands, appearing in August from Atria, she explores a different terrain.

Fans who know Gregory through bestsellers such as The Other Boleyn Girl won’t find this territory entirely unfamiliar. Like her fictionalized biographies, Tidelands is shaped by a reverence for British history and a commitment to chronicling the nature and impact of women’s lives. Rather than anchoring this story in the life of a historical figure, however, the author used a wholly fictional protagonist this time around.

For Gregory, the change has been exhilarating. “There’s a great deal of invention involved in writing fiction based on real people, but of course you’re stuck with recorded fact and chronology,” she tells me from her home in Northern England. “Writing about purely fictional characters in Tidelands allowed me to step more fluidly in and out of the historical record. That’s been exciting, and I’ve felt incredibly free.”

The idea for the series that Tidelands debuts arose in part from an unlikely source: Gregory’s rereading of John Galsworthy’s Forsyte Saga series from 1922. What captured her interest was a brief, mostly overlooked moment in the story in which the wealthy Soames Forsyte decides to explore his family’s roots. Rather than a sense of connection, his visit to the Somerset field he believes the Forsytes once farmed emphasizes his distance from the family origins.

“Soames has such a sense of being a fish out of water there,” Gregory explains. “The family has moved so far in terms of class, among other measures, that he’ll never really understand their past. It’s a tiny section of the book, but I thought it was terribly interesting. As a historian, I always want to know the story behind the story.”

Gregory’s own family, she realized, followed a trajectory similar to—if less dramatic than—that of the Forsyte clan. “As so many family histories do, mine starts in poverty,” she says. “My ancestors lived as poor people in a depressingly flat and muddy part of England. They gradually rose out of the mud to become bourgeois enough that when I came along, I had the luxury of being able to go to university.”

Gregory says she decided that she wanted to create a fictional family and trace its transformation in the course of successive generations. “I’m interested in how the fortunes of an ordinary family reflect the fortunes of a nation—and in the way a fictional story can tell a historical truth,” she adds.

As in her other books, Gregory put a woman at the heart of her narrative. Alinor Reekie, the protagonist of Tidelands, is a midwife, herbalist, mother, and wife to a husband who’s vanished, perhaps dead (but perhaps not). Gregory envisioned her as a “marginal woman, in every way you could imagine,” she explains. “Like so many women throughout history, Alinor is someone trying to lead a steady life in shifting circumstances. She is married but has no support from a husband. She lives in a place where land turns into sea and a time when women are increasingly demonized. She is a midwife at a time when female healers are being pushed out of an increasingly male profession. She works with herbs, an expertise that is simultaneously dying out and coming under fire for its possible connection to witchcraft. In everything she does, she has to walk a very narrow line. I think a lot of women recognize that feeling.”

Tidelands is set in the mid-17th century, when the English Civil War is roiling England and the deposed Charles I is attempting to bargain or plot his way out of captivity on the Isle of Wight. Historic clashes between Royalists and Parliamentarians, and Catholics and Protestants, take place far from Alinor’s isolated Sussex home, yet the country’s tensions nevertheless reverberate through her life. Her brother Ned longs to be off fighting for limits on the monarch’s power and a more equitable distribution of wealth and property. Her son is chosen to serve in the household of the local squire with Royalist sympathies. In the book’s opening scene, Alinor helps shelter a Catholic priest who has traveled in disguise from France in the hopes of helping the king escape.

The impact of national conflicts notwithstanding, Alinor’s life is parsed not in grand events but in minute calculations: whether she has enough food for both the endangered priest and her growing son, where she’ll get the money to provide her daughter a dowry. Gregory scoured period documents and historical studies to write accurately about Alinor’s experience of poverty. “The prices in the market are accurate not just to the time but also to Sussex at that time,” she notes. “Tiny price differences between one location and another really mattered.”

Gregory feels fortunate to live in a time when historic records are increasingly available in digital form and emphasizes her appreciation for the scholarly work that lays a foundation for her research: “History used to be about the elite, about what kings did when they got up in the morning. Only in the past 50 years or so have we gotten past that kind of snobbery. Now we have fine historians examining the lives of ordinary people, making the experience of women visible, and illuminating subjects such as witchcraft and midwifery. Though I express it in fiction, I’m glad to be part of a wave of social history that says, ‘Yes, this too is interesting.’ ”

For all of its loyalty to accurate quotidian detail, the novel is also richly atmospheric. In the tidelands of its title, the Sussex wetlands that are home to Alinor and her family, Gregory evokes a landscape where paths that exist one day disappear the next and accurate maps can never be drawn. Asked what inspired this setting, Gregory explains that she lived and worked near a wetlands nature reserve in her early 20s. “Most summer days, I would go with my books to the reserve, observing the colony of little terns that populated the shingle bank there,” she recalls. “I didn’t realize it at the time, but that landscape was really seeping into my imagination. It became one of those things that gets banked in a writer’s memory, ready to be remembered and used later on.”

This liminal, unchartable place is a fitting metaphor for the England in which Alinor lives—and, in a sense, for Gregory’s work on the book. When she first pitched the idea of a family saga to Atria, some elements of the narrative remained unclear. “I knew it would be a series about a family who would rise from poverty to bourgeois status, who would travel, who would form a trading company and have links to America and China. I could see stories that I wanted to tell about them extending up to 1920. But there were a lot of things I couldn’t yet pin down. I probably drove my publishers mad.”

As Gregory drafted Tidelands, the details solidified, but the timeline shifted. Initially planning to move from the 17th to the 18th century in the series’ second book, she realized that she was not ready to leave Alinor’s family. “I didn’t expect to have such an interest in Alinor’s son Rob, who we see as a boy in Tidelands,” she says. “How is he going to turn out? I’m developing that in book two.”

Of such shifts, Gregory says: “It’s very intuitive. I’ve written so many books that I’ve learned to trust the process. These characters are very alive to me. I have faith in what emerges as I watch them, even when it takes a very different direction than I expected. I don’t always know what I’m doing, but I know it’s going to come.” She pauses, smiling. “I admit, I’m touching wood on that, just to be on the safe side.”

Suzanne Fox is a writer, speaker, and freelance editor in North Carolina.