Mary Bly was born in Minnesota in 1962, the daughter of Robert Bly, winner of the American Book Award for poetry, and Carol Bly, a short story author. She was the inspiration for her mother's essay "The Maternity Wing, Madison, Minnesota," which was published in the anthology Imagining Home: Writing From the Midwest. Her godfather, James Wright, wrote a poem especially for her, which he included in his Pulitzer Prize-winning Collected Poems. Bly has three younger siblings, Bridget, Noah, and Micah.

The Bly family did not own a television, but did own over 5000 books. Robert Bly often read to his children, choosing to expose them to classics such as Beowulf instead of more traditional children's fare. Even at a young age, however, Mary Bly was fascinated with romance. To entertain her siblings during a snowstorm, she built a puppet show, complete with lights, that featured a romance. Several years later, after discovering the romance novels of Georgette Heyer in her local library, Bly convinced her father to allow her to read one romance novel for each classic novel she read.

After graduating from Harvard University, Bly went on to attain an M.Phil. from Oxford University and a Ph.D. in Renaissance studies from Yale University. She is a tenured associate professor lecturing on William Shakespeare at Fordham University in New York City. She has served as Director of Graduate Studies in the English Department, as well as head of Fordham's Creative Writing Program . In addition to publishing an academic book with Oxford University Press, she has published an academic article on 17th century drama in The Publications of the Modern Language Association, the most prestigious journal for English literary studies.

While attending the University of Virginia on a humanities fellowship, Bly began writing romance novels. Her second career began when her husband wished to postpone having a second child until they had paid off their student loans. To speed the process, Bly followed her parents' examples and wrote a story to send to a publisher. Two publishers bid for that novel, Potent Pleasures,, netting Bly an advance that paid off her student loans in full. As she was at the time an untenured professor about to publish her first academic work, Bly made the decision to publish her fiction books under a pseudonym, Eloisa James, out of fear that her colleagues would not take her seriously as an academic if they knew of her side writing. Her books have since been translated into 9 languages and have become hard-cover bestsellers in the Netherlands and Spain. She has had 12 New York Times bestseller and 16 USAToday bestsellers.

Bly's first three novels, the Pleasures trilogy, were published in hardcover by Dell, a plan with which Bly did not fully agree. Following the publication of those three novels she bought out the remained of her contract and moved to Avon, where her books are now published in mass market paperback format. She believed that marketing her first works as hardcovers was not a truly successful plan and hoped to have more success with the mass-market paperbacks.

Inspiration for her novels comes in part from her academic career, as plays or facts discovered during her academic research often spark ideas for fictional plots. Her novels, which are set in England's Regency period (1811-1820), often have references to Shakespeare or include pieces of 16th-century poetry or other tidbits she has found while researching her academic papers. As she spends much of her day teaching about or reading early British English, she feels that the language choices she makes in her novels are more authentic. Although Bly has attempted to write a contemporary romance, she chose not to finish the manuscript because of difficulty writing in a contemporary voice.

The characters in Bly's novels often dispense with the typical romance novel stereotypes, with the novels featuring female characters who are plump and even a hero who annulled a marriage because of impotence. Her heroines are usually surrounded by very good female friends or sisters, as Bly finds those relationships important in her own life. Most of her novels are part of a trilogy or set of four novels which focus on a set of interconnected characters, and explores the relationships between those characters as well as that of the hero and heroine.

For several years Bly's second career remained a secret, and she disguised herself by wearing contacts instead of her normal glasses when she attended functions as Eloisa James. After her first New York Times Bestseller in 2005, Bly realized that her readers liked her writing regardless of its genre, and that by keeping her identity a secret she was implying that she was ashamed of her work and of her readers. At a February 16, 2005 faculty meeting, Bly outed herself to her colleagues, revealing her alter ago and offering copies of her novels to her fellow professors. Once she had officially "come out", she submitted an op-ed to The New York Times defending the romance genre.

Bly credits her success in dual careers to being "very, very organized." Lacking the time to write every day, Bly often writes upwards of 20 pages at a time. On her days at home, Bly schedules time to work on both her fiction and her academic works. When possible, she does not work when her children are at home. Bly usually does not teach in the summers, giving her more time do devote to her writing (both academic and fiction).

Her large workload leaves her little time to research some of the historical aspects for her novels. She has hired a research assistant to confirm details of topics she would like to include in a novel.

Bly's father and stepmother, Ruth, are very supportive of her romance writing. Her mother, however, publicly wished that her efforts were focused towards more literary works. Despite that, Carol Bly also supported her daughter, contributing a "nifty crossword puzzle" to the Eloisa James website.

Bly is married to Alessandro Vettori, an Italian knight (or cavaliere) who is also a professor of Italian at Rutgers University, whom she met on a blind date while she was at Yale. They have a son and a daughter. The family live primarily in New Jersey, but spend summers in Tuscany visiting Alessandro's mother and sister.

Academic Works as Mary Bly

• Consuming London: Mapping Plays, Puns, and Tourists in the Early Modern City

Romance novels as Eloisa James

The Pleasures Trilogy

The Duchess Quartet

The Essex Sisters Series

The Desperate Duchesses Series

Novellas in Anthologies in collaboration

The Happily Ever Afters