Anne Lister has been having a moment. Widely acknowledged as one of the first public lesbians of the modern era, she blazed a trail through 19th-century England, acquiring lovers, books and properties and traveling throughout the world. She left behind a diary of some 5 million words, now parsed and studied by those seeking insights into her life and times. She was played by a swaggering Suranne Jones in the acclaimed BBC/HBO miniseries “Gentleman Jack,” which ran from 2019 to 2022.

But when Emma Donoghue decided to take on Lister in her new novel, “Learned by Heart,” she wanted to focus on a lesser-known chapter of Lister’s life, a formative period before the girl became a woman. Donoghue, a prolific historical novelist who was nominated for an Oscar for adapting her own book, “Room,” into a 2015 film, zoomed in on the 14-year-old Lister’s brief time in a York boarding school — and her torrid romance with her roommate, Eliza Raine.

Lister, a precocious tomboy who seemingly knows something about everything, and Raine, a half-Indian heiress born out of wedlock, were fellow outcasts who found each other at the Manor School in 1805. Their first love left Lister emboldened, while its premature end left Raine devastated.

For Donoghue, who poured her usual volumes of research into the novel, Lister proved fine company. But Raine was the real revelation.

“Lots more people have heard of Lister than was true even five years ago,” Donoghue says over video from her home in London, Canada. “In the wonderful ‘Gentleman Jack’ series, she’s a really vivid character in her 40s, and more and more of her work is being transcribed and published. But Eliza remains this truly mysterious figure, and she’s so interesting. She’s got the fortune and the education and the beauty, and yet she’s from India and she’s illegitimate, which I think really would’ve counted against her at that time.”

When they first meet in the novel, Raine is a little puzzled by her new friend. “I’m rather an enigma even to myself,” Lister tells her. “Nature was in a funny mood the day she made me. Perhaps I’m the connecting link between the sexes.” Soon, however, Raine grows enchanted. As Donoghue writes, “What’s between them grows like a creeper that covers the ugliest bricks and drainpipes in living green.”

Donoghue depicts this youthful affair as an all-consuming force, hidden among the regimented lessons and strict propriety of the school. From the start, she lets us know Raine won’t emerge unscathed, mixing in desperate letters written later from an asylum among the present-tense ecstasy of the relationship. “I was only 14 when I first tasted that intoxicating draught,” Raine writes Lister in one missive, “and I must have drunk too deep.”

Known for her relentless digging through historical records and archive material, Donoghue also relied on her own emotions and memories as an adolescent realizing she was queer in 1980s Ireland.

“With historical fiction, I think it’s often underestimated how you bring in things from different eras — including your own life,” she says. “So with this novel, I really tried to channel my being 14 in a Catholic convent school and falling madly in love with a girl, and how it just completely rocked my world. I didn’t think I was actually going to hell, but I did possibly think I would be sent off to the psychiatrist or the priest. … So two centuries after Eliza, I think many young queers still have that feeling of, ‘Oh, my God, this has transformed and filled my life with joy, but also terror.’”

Donoghue, 53, doesn’t always live in the past; “Room,” the story of a young woman and her son held captive by a madman, is a contemporary tale, and probably her most popular and best-known novel. But she often finds herself mining history. “Slammerkin” (2000) was inspired by an 18th-century newspaper story about a servant who murdered her mistress in Wales. “The Sealed Letter” (2008) recounts a 19th-century British divorce case. “Haven” (2022) is about monks following a mystical vision in 7th-century Ireland.

“It’s a funny business,” Donoghue says. “You’d think if I really cared about the truth so much, I wouldn’t be interested in fiction and vice versa. But I seem to like them both.”

Naturally, she’s happy to be plying her craft at a time of unprecedented access to information — digitized newspaper scans; helpful social media contacts; transcribers just a mouse click away. “I reached out to one guy on Twitter about a quote, and he looked up the source and transcribed it and sent it back immediately,” she says. “That kind of almost telepathic, rapid contact with a friendly stranger wasn’t possible 20 years ago even.”

Inspired by history and abetted by modern technology, “Learned by Heart” is nevertheless preoccupied with timeless things, revealing how little has changed.

“Writing about first love was hugely enjoyable,” Donoghue says. “You always want your characters to be going through some astonishing change, and that’s easier to achieve when they’re 14. When your characters are older, you have to work a bit harder on slapping them awake.”

Lister, it would seem, slapped a lot of people awake. “Learned by Heart” tells the story of the first strike.