In the final chapter of her book Flat Earth: The History of an Infamous Idea, Christine Garwood estimated “there are probably no more than a few thousand flat-earth believers alive in the world today and fewer still who would be willing publicly to declare their conviction.” That was in 2007. Fifteen years later, flat-earth conventions pull in hundreds of attendees, social media websites pullulate with thousands of flat-earth videos, and the globe is populated by millions of people who believe—or are at least willing to tell pollsters that they believe—the earth is flat. In Off the Edge, Kelly Weill, a journalist for The Daily Beast who specializes in covering extremism and disinformation, both updates the history of flat-earthery to encompass the age of the internet and explores the deepening immersion of the flat-earth movement in a disturbingly toxic conspiratorial milieu. Alert, informed, and up-to-date, Off the Edge is aptly describable as on the ball.

The first three chapters provide a capsule history of the flat-earth movement from 1838, when Samuel Birley Rowbotham decided that the Old Bedford Canal in Cambridgeshire, England, was the ideal place to demonstrate the flatness of the earth, to 2001, when Charles K. Johnson, the lonely last president of the International Flat Earth Research Society, died. Although Weill’s account accords with the detailed histories provided in Garwood’s Flat Earth and Robert J. Schadewald’s The Plane Truth (2015), it is largely based on her research in the original sources, enabling her to provide information and insight not present in its precursors. Her account is also amusingly punctuated by her personal reactions: for example, she writes, of Lady Blount’s flat-earth wish-fulfillment novel Adrian Galilio (1901), “I adore this bizarre little book,” and proceeds to describe how “I conscripted a friend to record a version of a song” included in the novel “with lyrics railing against godless ‘globeites’” (34).

What resurrected the flat-earth movement in the twenty-first century was the rise of the internet: “the sudden surge in available information gave rise to a rich conspiracy culture” (79), with figures such as Mike Adams and Alex Jones—not themselves flat-earthers—setting the tone. The comparatively sedate and scholarly Flat Earth Society, established online by the pseudonymous Daniel Shenton in 2004, was soon eclipsed by extremist flat-earth entrepreneurs such as Eric Dubay, who “eventually accused the Flat Earth Society of being a fake group designed to discredit the movement, due to its more modest conspiratorial stances” (94). However, it was not just the new platform of the internet that encouraged flat-earthery; the social media company algorithms that suggest new material for users to peruse often present them with a series of increasingly crazy conspiracy theories. Facebook and YouTube have attempted to fix the problem, with imperfect success, but the damage was already done.

A fair amount of Off the Edge is devoted to recounting the damage. Weill is sympathetic to Nate Wolfe, a pastor who lost his job over his flat-earthery, and to “Mad Mike” Hughes, a daredevil who lost his life while attempting to test his flat-earth beliefs in a home-made steam-powered rocket. (There are conflicting reports about whether Hughes was a sincere flat-earther, which Weill assesses judiciously.) Flat-earthers are often socially isolated on account of their beliefs; although the modern flat-earth movement is sustained partly by a sense of community among beleaguered believers, factions and feuds among them are rife. Those who forsake the flat earth face a further set of problems. But the rest of us suffer from flat-earthery too. Aggressive and confrontational proselytization by flat-earthers—which they call “flat-smacking”—is not unknown, and there have been sporadic threats of violence against Facebook and YouTube over their moderation of their flat-earth users, as Weill describes.

Worse, though, is the way in which flat-earth beliefs are increasingly immersed in a toxic conspiratorial milieu that now seems to encompass anti-vaccine sentiments, QAnon, and—inevitably—anti-Semitism. The Wisconsin pharmacist who deliberately ruined a batch of COVID-19 vaccines? The Californian who was smoking marijuana while invading the United States Capitol during the January 6, 2021, insurrection? The habitués of a neo-Nazi website who gleefully adopted “usernames like InterJew, 3rdRicht, and SouthernFascist” (190)? Flat-earthers all, apparently. Weill’s discussion of these conspiracy beliefs and their adherents is often harrowing, so her wry humor, present throughout the book, is particularly welcome here. After acknowledging the Indic roots of Nazi and neo-Nazi emblems such as the swastika and the sonnenrad, for example, she explains, “If you wear a swastika T-shirt on a public stroll in the United States, you’re probably a jerk, not a Jain” (182).

Toward the end of her book, Weill offers a few thoughts about combating the flat-earth movement. She plausibly urges that social media companies such as Facebook and YouTube need to take further action: not merely fact-checking, which is of dubious efficacy, but fixing their recommendation algorithms and, when necessary, banning particularly egregious characters, such as Alex Jones. Such actions will be of only limited effectiveness, but individual interventions are still necessary. In these, Weill suggests, “Maybe we need to approach debunking less like a debate and more like holding a friend’s hand” (212)—so a little empathy makes the world go round? Unfortunately, the ensuing discussion is centered on just two case studies. Weill would have done well to consult Lee McIntyre’s How to Talk to a Science Denier (2021), which is based not only on McIntyre’s own conversations with flat-earthers but also on a review of the relevant psychological literature, for a model of a systematic treatment.

Not to be unduly captious, but there are a handful of minor problems with the book. The description of a rockoon as a “rocket attached to weather balloons that would carry it upward after the rocket fuel burned out” (153) is backward—the rocket is fired after the balloons carry it as high as they can—which suggests a deficiency in Weill’s grasp of basic physics. Toward the end of the book, Weill speculates that flat-earthers are motivated in part by a desire for a cozy cosmos; perhaps so, but a similar diagnosis is available to flat-earthers, who have been known to argue that mainstream astronomy’s insistence on the vastness of the universe is intended to scare, and thus enable control over, the public. And it is annoying that there is no index. But these, again, are minor problems. Weill’s Off the Edge is not only a worthy successor to Garwood’s Flat Earth and Schadewald’s The Plane Truth but also a worthwhile contribution in its own right.