The only truly poetic act Percy Bysshe Shelley ever accomplished was saving his wife Mary from bleeding to death by packing her in ice while she was miscarrying. Otherwise, he was something of a wimp. He fainted during a reading of The Rime of the Ancient Mariner. His politics were revolutionary but, like most of the English Romantics, his poetry was overrated. “Out of the day and night / A joy has taken flight.” Drivel!

Mary Wollstonecraft Shelley, née Godwin, is underrated in inverse proportion. In her great novel Frankenstein; or, The Modern Prometheus—as well as the books Mathilda (1819) and Valperga: or, the Life and Adventures of Castruccio, Prince of Lucca (1823)—she managed to unite the Romantic novel’s interest in the sublime with a seriousness both political and philosophical. She not only achieved these feats while living with the peevish Percy, but did so despite the long shadows of her parents, both famous geniuses.

Mary Wollstonecraft, author of A Vindication of the Rights of Women, died only a few days after her daughter was born. William Godwin, an early advocate of anarchism, survived a great deal longer. He’d hoped to have a son named William, but after his wife’s death Godwin was left to raise both the newborn Mary and another infant, Fanny Imlay, whom Mary Sr. had borne out of wedlock. Godwin took over Mary’s education and raised her to be a rigorous and unorthodox thinker. Their relationship hit a big patch of rocks, however, when his own student started hitting on his teenage daughter. Before long Percy Shelley had persuaded Mary to run away from home, and had taken her stepsister Claire Clairmont (Godwin had remarried) with them.

In every aspect that Percy is overrated, Mary shines. But the heroic ice bath is not included in the new biopic Mary Shelley, directed by Haifaa Al-Mansour (Wadjda) and written by Emma Jensen. There is no mention of the couple’s fascinating travels through France during the first years of their relationship. There is an entire sister—Fanny Imlay, who dramatically committed suicide—who is not in the movie. Percy’s first wife kills herself in the wrong year. Mary even theatrically proclaims herself to be the wrong age when she presents her manuscript to a publisher.

All these weird omissions and errors pale into insignificance compared to the total absence of text in the movie. Jensen’s script has turned the early years of Mary Shelley’s life into a pure psychodrama determined by events. Percy lures her away; Percy cheats on her; Percy doesn’t know how to comfort her when her baby dies. Byron is rude to her and her dad is unsympathetic.

Although we do see her witness a frog getting galvanized into a little postmortem dance—famously the inspiration for her reanimated monster—Mary Shelley’s writing of Frankenstein is portrayed as a metaphor for her own woes. The monster is lonely and ravaged by grief, like her. Percy is like Frankenstein himself, Polidori literally says out loud at one point. He’s a narcissist who cannot see the, uh, monster he has created with his cruelty.

My sympathy goes out to anybody making a biopic of a writer. It’s not easy to turn such a solitary, stationary activity into interesting subject matter for the camera. But Mary Shelley falls into exactly the same trap as the recent film The Young Karl Marx, by focusing entirely on the facts of the author’s life and barely digging into the true reason that the subject is important, which is their writing.

Frankenstein can be read as a glorious political allegory. The monster rages not only against his creator, who flees from him in horror, but also against all institutions, symbolizing in one respect the “monstrous” horde of the working classes who rise in consciousness against their masters.

Consider this excerpt from a speech by the creature to Frankenstein:

Remember that I am thy creature, I ought to by thy Adam, but I am rather the fallen angel whom thou drivest from joy for no misdeed. Everywhere I see bliss from which I alone am irrevocably excluded. The desert mountains and dreary glaciers are my refuge. I have wandered here many days. The caves of ice, which I only do not fear, are a dwelling to me, and the only one which man does not grudge. These bleak skies I hail, for they are kinder to me than your fellow beings.

The creature has read Paradise Lost, and here his Adam becomes a fallen Lucifer. He has wandered, despised, for many days in the wilderness. His only comfort is in the sublime—caves of ice, bleak skies, dreary glaciers—which shows him how meagre man’s gifts are in the face of immeasurable nature. He speaks like Wordsworth: “Of aspect more sublime; that blessed mood / In which the burden of the mystery / In which the heavy and weary weight / Of all this unintelligible world, / Is lightened.”

Of these perfect lines Mary Shelley seems to understand little. The best parts of the film come in interstitial shots that establish atmosphere. Mist plays in the dark woods; dust clouds an empty room; smoke drifts across the moon. But the dialogue between these characters displays nothing of their genius. (I will admit Percy was intelligent.)

Douglas Booth plays Percy Shelley. Booth is no stranger to period drama, having played Bingley in Pride and Prejudice and Zombies and Nikki Sixx in an upcoming Mötley Crue biopic. But there is nothing in his performance that helps us understand why an intelligent young woman would run off with him. Tom Sturridge as Lord Byron is equally one-dimensional. They’re pretty boys with no evident talents at all. The women actors of the movie are by far their superior. Bel Powley plays Claire Clairmont, Mary’s stepsister who has a child with Byron, with pluck and bravery.

Elle Fanning as Mary Shelley is the movie’s only real grace. She has been given a poor script to inhabit. As a beautiful young actor, she could easily have been swallowed up by the teen drama lines she must deliver, but they don’t beat her. She brings a steel and nerve to the role that takes the movie into almost literary places. If the film had taken place more in Mary’s head, and played up the textural drama behind those night sky shots, then Mary Shelley could have had a chance at living up to its subject’s greatness. But Mary Shelley’s gifts are not to be found in this movie.