Fifteen seconds is all you need. Point your phone camera to a shelf and hold up your favourite book, or three. Add a trending soundtrack, a caption, a couple of hashtags – #BookTok #FYP. Throw a pandemic into the mix and you have the formula: you can make a book review go viral. Stuck inside during Sydney’s Covid lockdown, I fell down the endless TikTok abyss, where I found BookTok: the app’s reading corner that has amassed more than 26bn views. There, I spent more time watching people talk about books than actually reading books myself. One of those people is Cait Jacobs, a book blogger based in New York. Jacobs joined BookTok under the handle @caitsbooks in December 2019. Three months later, she started posting content to a small follower count of 100. That number has since skyrocketed to more than 240,000. Her videos range between 10,000 to more than 1m views. One about LGBTQ+ representation in books has been viewed more than 8m times. “I really thought when I started that no one would see my videos,” she tells me. “I’m an introvert – I have social anxiety going to a grocery store. So connecting to so many other readers is a shock.” On a platform like YouTube or Instagram, you have to actively seek out book-related content. On TikTok, it can be stumbled across. “Videos filter to the For You Page seamlessly,” Jacobs explains, of the assemblage of new TikToks users scroll through as soon as they open the app. “And the audience it reaches is not just readers”. Hence the staggering numbers. Behind the ambiguity of the TikTok algorithm is a sense of organic growth, stronger than that of any other platform. My For You Page is filled with a mysteriously curated mix. It is individualised – perfectly aligned to my interests, and slightly terrifying if you think about it too deeply. The audience that scrolls beyond the FYP – through BookTok accounts and tags – will pick up on patterns. Many videos follow “formats” likely to go viral. Recommendation lists are a staple example, where the emotion of a popular song on the app is thoughtfully paired with the books being recommended. A stack of novels featuring “angsty enemies-to-lovers romance” would be perfect to the punch of Good 4 U by Olivia Rodrigo, for instance. Or, a selection of “books guaranteed to make you cry” listed off to her heartbreak ballad Drivers License. One of my favourite video formats is less popular, and involves a creator sharing the plot of a book as though it were a real story of their own. Elizabeth Cayoutte – aka @bettysbooklist – pioneered this. Looking down the barrel of her phone camera, she says: “Someone has died at the school costume party. My friends and I take parenting very seriously, and while we have our secrets, I assure you that it was an accident. So why won’t anyone believe me?” After a tantalising moment of shock and intrigue, the video cuts to the cover of Big Little Lies: the Australian domestic mystery novel published in 2015. Other TikTokers such as Jacobs jump across various formats, from sharing guilty pleasure tropes and relatable bookish experiences, to assuming what her audience’s “favourite book says about them”. Often featured in her videos is Leigh Bardugo’s young adult fantasy duology, Six of Crows. It is a series I also call a favourite, so we share in a little squeal about it over the phone. “Six of Crows always gets people talking,” Jacobs says. “I think it’s the mix of a rich fantasy world and a diverse ensemble of characters.” Though YA novels such as Six of Crows, E Lockhart’s We Were Liars, Kiera Cass’s The Selection and anything written by Sarah J Mass thrive on BookTok, broader genres are not forgotten. “YA fantasy is a big one, but so are mysteries and classics.” Jacobs says there is also a huge appetite for “spicy” and “smutty” books; books that are sensual, erotic, or both. “BookTok is a place where everyone is comfortable,” she says. “Because everyone is eager to share their reading, and delve into what they want from their plots, characters and worlds. And all it takes is a short video.” These short videos have been noticed beyond the world of BookTok - 26bn views of the BookTok hashtag means a viral five-second clip can impact sales worldwide. The Guardian has coined it the BookTok effect; where books are hyped on TikTok, and top bestselling charts soon after. Jacobs says it is so prevalent, she can “point directly to the videos” that catapulted certain books to popularity. “Selene from @moongirlreads created a spike in sales of The Song of Achilles by Madeline Miller. And Ayman, from @aymansbooks, made it impossible for readers to get their hands on The Invisible Life of Addie LaRue by VE Schwab after her video recommending it.” Booksellers have caught on, with Barnes & Noble in the US featuring a “discover popular BookTok books” category on their website, and displaying a BookTok table in stores. “It is surreal,” Jacobs says. “It is special, because BookTok has such a wide reach and audience around the world, but it is just a community who love to read and talk about it. “It’s something I never would have imagined could happen.”