Jane Austen’s face — demure, bonneted, with a few stray curls over her forehead — peers out pensively from the new British 10-pound note, debuting this fall to mark the bicentenary of her death. The bill superimposes her image over a stately mansion surrounded by vast gardens, with a horse and carriage in the foreground. The quotation below comes from “Pride and Prejudice”: “I declare after all there is no enjoyment like reading!”

This is the Jane Austen we think we know: conventional, proper, unthreatening, writes Oxford professor Helena Kelly in “Jane Austen, the Secret Radical,” her new critical reassessment of the author. In fact, all the standard tropes about her are wrong, or at least misleading. The iconic image from the BBC remake of “Pride and Prejudice” — Colin Firth as Mr. Darcy emerging, dripping wet, from the lake at Pemberley — exists nowhere in the novel. What little we know of Austen’s biography is likely to be false, tainted by the desires of her family to make her appear both less serious about her writing and less political than she really was. Even the quote that appears on the 10-pound note should be understood ironically: It’s spoken by a character who only pretends to be reading to impress a man. As soon as she’s said it, she throws her book aside.

Kelly argues — passionately and engagingly, if not always convincingly — that modern readers have failed to read Austen as she was meant to be read: in the context of her historical moment. She was born in 1775, just after the American Revolution began, and died at the tragically young age of 41, after an illness. (Kelly suggests that her death may have been hastened by a doctor who gave her a hefty dose of laudanum, a standard treatment at the time.) Britain and France were at war almost without a break from 1793 until 1815 — the period when Austen was probably writing her novels, which were published between 1811 and 1817. Between 1812 and 1815, Britain was also at war with America, the colony that had newly revolted.

[‘Eligible’: Curtis Sittenfeld’s modern retelling of ‘Pride and Prejudice’]

Wartime Britain was a totalitarian state, Kelly writes, “with the unpleasant habits” that such states exhibit, particularly regarding intellectual life. Formerly innocuous lines of thinking were newly defined as treasonous; the publishers of radical political writers were prosecuted; booksellers and newspapers were threatened; letters were censored. The aim was “to terrify writers and publishers into policing themselves.” Some, like Sir Walter Scott, took refuge in historical or foreign settings. Indeed, Austen was the only novelist of her period to set her work “more or less in the present day and more or less in the real world,” even depicting her characters walking on actual streets. In so doing, she offered trenchant commentary on the social and political issues of the day. But like writers in communist Eastern Europe, Kelly argues, she wrote in a kind of code, “anticipating that her readers would understand how to read between the lines. . . . The trick was never to be too explicit, too obvious.”

Kelly’s task, as she sees it, is to decode Austen, revealing her as the “secret radical” she truly was. Her critical method is to focus microscopically, generating meaning from the smallest details of the novels — names of people and places, lines of poetry quoted, the etymology of words — juxtaposed with historical context. In a probing reading of “Mansfield Park,” for instance, Kelly traces a long strand of allusions and associations to argue that slavery — specifically, the Church of England’s complicity in it — is the backbone of the novel. (This isn’t a new reading; Paula Byrne, drawing on the work of other scholars, makes a very similar case in “The Real Jane Austen,” her 2013 biographical study.) Similarly, Kelly argues that the newly introduced system of enclosure, by which land formerly accessible to the public was restricted as private property, is the hidden focus of “Emma.”

It’s no secret to any observant reader that Austen frequently drew on her social and political context, usually to critique it. The Bennets in “Pride and Prejudice” refer over and over to the tyranny of the “entail” on their estate — the law requiring that it be handed over to a distant male relative rather than inherited by a daughter. But it doesn’t necessarily follow that Austen meant for that novel to be understood as “a revolutionary fairy tale, a fantasy of how, with reform . . . society can be safely remodeled.” In fact, it detracts from Austen’s enormous artistry to say she did. To perceive her “courtship plots” as fluff is to underestimate her work. As Kelly herself acknowledges, “Marriage mattered because it was the defining action of a woman’s life; to accept or refuse a proposal was almost the only decision a woman could make for herself.”

Through her extraordinary psychological insight, brilliant characterizations, deft command of satire and humor, and — indeed — political astuteness, Austen spun her “courtship plots” into complex investigations of human nature, as well as of social inequality, financial dependency and other pressing issues of her time. To discover that doesn’t require complex decoding — merely thoughtful reading. We don’t have to subscribe to Kelly’s vision of Austen as a political revolutionary to understand her as a radical, though not a secret one. That her novels prioritized the true circumstances for women in her era is radical enough.

Ruth Franklin’s most recent book is “Shirley Jackson: A Rather Haunted Life,” winner of the National Book Critics Circle Award for Biography in 2016.

Read more: A modern retelling of ‘Emma,’ by Alexander McCall Smith