Concerned that screen time is cannibalizing reading time? Consider this: 2015’s top-selling humor book for adults, per Nielsen BookScan, was written by a YouTube celebrity. The #1 new book in children’s humor this year? Ditto. And the same goes for three of the 10 bestselling memoirs released in 2015: all of the authors got their starts posting videos online.

The YouTube-to-book deal isn’t new, but in 2015, the phenomenon hit critical mass, with multiple books debuting on PW’s bestseller lists, many of them staying put for weeks.

Simon & Schuster leads the phenomenon with its Atria/Keywords imprint, which is dedicated to publishing books by online stars. Carolyn Reidy, president and CEO at S&S, believes that YouTube authors draws new readers who, having seen the personalities on the web, want to own a small piece of them. Online videos are, by their nature, intangible; a printed book, on the other hand, is anything but.

Keywords published its first title, the YA novel Girl Online by Zoe Sugg, toward the end of 2014; it has sold more than 109,000 print units to date, 79,000 of them this year, according to BookScan. 2015 releases include memoirs by Connor Franta (A Work in Progress, 175,000 print units), Joey Graceffa (In Real Life, 100,000 print units), and Shane Dawson (I Hate Myselfie, 89,000 print units).

Other S&S imprints have had success with books from digital celebrities, including Gallery, whose Selp-Helf, a humor title by Miranda Sings (alter ego of actor Colleen Ballinger), has sold more than 132,000 print units.

Each of these authors boasts online subscribers numbering in the millions, but online popularity doesn’t necessarily mean mega book sales. PewDiePie, a Swedish vlogger who films himself playing and commenting on video games, is one of the most popular YouTubers, with 40 million subscribers. Razorbill published PewDiePie’sThis Book Loves You, a compilation of tongue-in-cheek inspirational sayings and illustrations, in October; it’s sold about 48,000 print units, a sign that his brand of humor may not translate into print as well as some other video stars.

By contrast, The Haunting of Sunshine Girl by Paige McKenzie, with Alyssa Sheinmel, which Weinstein published in May, has sold more than 40,000 print units. It’s based on a YouTube channel with 1% of the subscribers PewDiePie has, but that channel is a teen horror Web series, and the book, a YA horror novel, continues in that narrative vein.

Since so many YouTube subscribers are themselves teenagers, it makes sense that one of the biggest YouTube-to-book successes of the year came from a children’s publisher.

Random House Books for Young Readers released The Amazing Book Is Not on Fire by Dan Howell and Phil Lester, a lighthearted look at the YouTube duo’s online lives, in October. In two months, it has racked up sales of more than 127,000 print units. The secret to publishing a successful book by a YouTube celeb, publishers say, is that the person must have an actual story to tell.

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