Founded in 1947, the Folio Society was once a membership club known for publishing classic tomes and history books, with a customer base of predominantly “old white men”, according to its boss.

Now, however, more than half the people who buy its books are aged between 25 and 44, and it is selling more sci-fi and fantasy titles, boosted by BookTok and growing gen Z interest in “artisanal” editions.

The publisher, which produces illustrated editions with elaborate covers, has seen sales soar 55% since 2017-18.

Joanna Reynolds, chief executive since 2016, said: “We’ve completely changed the sort of books that we sell. We developed fantasy, sci-fi and more children’s. Particularly the fantasy and sci-fi have made a massive difference to us. Game of Thrones was literally a gamechanger … It made so much money for us.”

Reynolds recalled that, when she joined, “the business was in freefall by every metric. It was losing money, losing customers. It was in a mess.”

She ditched the membership model, opened the company to new audiences and started asking them what they wanted.

One of the answers was more sci-fi and fantasy. The genres are a growing market in UK publishing, achieving a record year for sales in 2023. In the past year, the Folio Society’s three bestselling titles across all age groups are Howl’s Moving Castle by Diana Wynne Jones, Dune by Frank Herbert and Jurassic Park by Michael Crichton.

Last week, the society published Children of Dune, the third in Herbert’s series, and sold more than 1,000 copies of the £80 book in 24 hours. Younger audiences buy more Tolkien and Game of Thrones, while older readers want James Bond novels and classics such as The Wind in the Willows and Rebecca.

“The under-25s market is now nearly as big as the over-65s,” Reynolds said. The society’s books are not cheap, ranging from £49 for a Wynne Jones to £1,000 for a limited edition The Lord of the Rings trilogy or the complete plays of William Shakespeare (both out of stock). The editions include bespoke illustrations, weighty covers and protective slip cases, with materials sourced from small suppliers such as Ludlow Bookbinders in Shropshire, letterpress printer Phil Abel in London, and Jemma Lewis Marbling in Wiltshire, which provides paper.

On social media, people have requested Madeline Miller’s novel Circe, which the society will publish next year. It has also tapped into the fandom around Wynne Jones. “There’s a massive community around Howl’s Moving Castle and they loved the illustrations,” Reynolds said.

She said listening to requests on social media and in surveys had bolstered sales. “We asked: what would you like us to print for our 75th [anniversary]? Wonderfully, they said The Neverending Story [by Michael Ende]. It’s done phenomenally well.”

One area of social media has been more influential than anywhere else, and not just for the Folio Society. BookTok – the area of TikTok dedicated to book-related content and recommendations – is now widely credited with boosting sales across the publishing industry and accelerating the careers of authors.

The society’s books, with their coloured paper, textured spines and illustrations, make them perfect for the visual media of TikTok and Instagram.

“BookTok is very good for us,” said Reynolds. Miller’s fantasy romance The Song of Achilles already had a significant online following when the Folio Society decided to publish an edition. One BookTok video of a user “unboxing” their copy went viral.

“We sold it out within weeks and we’ve reprinted it,” Reynolds said. “We have over two million views across [social media] platforms for Song of Achilles.”

Reynolds likened the appetite for “artisanal” books to the resurgence of vinyl. “We thought: will it work because we’re going to be more expensive than anything else? But it’s actually worked well. You can see that trend and love of art and artisanal. It’s a bit like going back into vinyl.”

UK sales of vinyl LPs increased for the 16th consecutive year in 2023, reaching the highest level since 1990.

Reynolds said that for younger generations, even those who mostly use e-readers, “they’re happy to pay for a wonderful edition of books they love. There’s something very exciting for them about the physical book.”