Let's start with a number: 37 million.
That's not page views or a figure about student debt. It's the number of subscribers to the PewDiePie YouTube channel.
PewDiePie is Felix Kjellberg, a video gamer with a legion of fans he calls "bros." He's the latest in a series of YouTube stars who have decided to publish a book.
"This Book Loves You" is a collection of aphorisms, bits of wisdom-slash-jokes, paired with photos and other visuals. It's coming out in October simultaneously in the U.K., Germany, Norway, Sweden and France and, in the U.S., from Razorbill, part of Penguin RandomHouse.
"Razorbill and Penguin US are excited to bring the words of PewDiePie to the American people in book form," Ben Schrank, president and publisher of Razorbill, said in a statement. "And with more subscribers than Taylor Swift and One Direction combined, Felix is without question one of the most influential stars of this generation."
PewDiePie isn't the first with a book deal. JennXPenn is coming. Grace Helbig, Shane Dawson, Mamrie Hart and Zoella already have published books of their own.
Grace Helbig, who's crossed over with a TV show on E!, has 2.4 million subscribers, and her book, "Grace's Guide: The Art of Pretending to Be a Grown-Up," hit the bestseller lists late last year.
British YouTuber Zoella (Zoe Sugg) had England's fastest-selling novel of 2014 with her debut, "Girl Online," selling 78,000 copies in its first week (never mind that it was revealed to have been ghostwritten).
In the U.S., Shane Dawson's essay collection "I Hate My Selfie" hit bestseller lists in March, with sales that publisher Atria said made it the fastest-selling book of any YouTube star. But he's got stiff competition with "You Deserve a Drink," the boozy memoir from YouTuber Mamrie Hart, which debuted on bestseller lists in May.
What these YouTube stars share is an ability to connect with fans, usually teens but also older readers, who often can prove elusive to traditional publishers. The robust YA market has shown that young readers can be extraordinarily devoted, once they connect to an author. Or, publishing hopes, to a YouTube star.
Publishing isn't exactly dying. The industry navigated some rough waters in the recession, but it's mostly slimmed down, consolidated and been buoyed by a couple of surprise bestsellers (50 shades of them, to be exact). And yet it's got some chronic maladies: distribution costs, diminishing e-book profit shares and the dominance of Amazon as a bookseller.
If PewDiePie's many bros (what he calls his fans) buy the book, it will certainly be a bounty for his publisher.
The bigger question for publishing, though, is if these projects are helping to create lifelong readers — people who'll want to buy more books — or if they're just looking for a physical manifestation of that one YouTube favorite they can have on a shelf for a while.
Book news and more: I'm @paperhaus on Twitter