Matrix by Lauren Groff review – thrilling trip into the mystic

Monasteries and convents make excellent crucibles: closed worlds in which the events of a novel are heightened, their tensions felt more keenly. Sylvia Townsend Warner’s The Corner That Held Them is a near-forgotten masterpiece set in a medieval nunnery, while Umberto Eco’s The Name of the Rose had metafictive fun mixing crime and semiotics. More recently, there’s been Christopher Wilson’s Hurdy Gurdy, James Meek’s To Calais, in Ordinary Time and, in a slightly skewed vision, Robert Harris’s The Second Sleep. Now we have Lauren Groff, author of the celebrated Fates and Furies, a sharp novel of New York life that drew comparisons to Gone Girl and was praised by Barack Obama. Groff’s fourth novel, Matrix, is something very different indeed: a strange and poetic piece of historical fiction set in a dreamlike abbey, the fictional biography of a 12th-century mystic.

Marie de France is a mysterious figure, a poet whose visionary lays and magical fables, written in Francien, a medieval dialect of Old French, are complex, sensual and self-lacerating. Groff has read these mystical poems and what limited historical records we have and has fashioned a life for Marie. We first meet our ungainly heroine aged 17, as she is cast out of her home; the illegitimate half-sister of Eleanor of Aquitaine, she is sent to a nunnery in England. She leaves behind the servant girl whose “frank and knowing body” provided Marie with endless pleasure. She is near-mad with love for her half-sister, whose presence lies heavily over her adolescent mind.

Related: Lauren Groff: ‘I often get very lonely because my job is very lonely’

Marie finds the abbey in a terrible state. The abbess is profligate and maladroit. The nuns’ faces “are skulls skinned of flesh in the dark dortoir”. Marie first kicks against the strictures of the convent, then decides to seize power herself. Soon, she is prioress, then abbess, and the formerly unproductive lands and delinquent tenants start making the abbey a place of great wealth. Like Madeline Miller in The Song of Achilles, Groff finds in the germs of the historical record whispers of hidden sexuality. “There is no mention of female sodomy in any of the books and the great angry moralists would have mentioned it if it were a sin,” Marie tells herself. Soon, all men are expelled from the lands around the convent and a great labyrinth is built to protect it from attack. The abbey becomes an island, the women providing each other with everything they need.

This island comes under attack: from jealous villagers, from a sex-crazed novice, from the church in England and in Rome. Marie – massive, majestic, wise – overcomes them all. Groff has written a beautiful, unclassifiable book, a queer history that recovers a great poet from the past and fills her with glorious, corporeal life. Marie wrote moral fables and that’s one way of understanding Matrix, although its lessons are intricate and obscure, its vision of a closed female state far from utopian.

• Matrix by Lauren Groff is published by William Heinemann (£16.99). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply