Matrix by Lauren Groff is an unusual novel about a shadowy figure in history, Marie de France, a 12th-century poet and mystic who spent much of her life in an abbey in France. At age 17, Marie is exiled from the court of her half-sister, Eleanor of Aquitaine, and sent to a moldering convent, where she quickly takes control. While the subject is something of a departure from Groff’s last book, her lucid writing gives the book a strong sense of place without losing its modern pace. Groff fills in the gaps in the historical record of this extraordinary woman and weaves together a story of female power and desire.