(NYTimes) - The heroine of Hank Green's debut novel, An Absolutely Remarkable Thing, is an art student in New York City named April May, who finds herself at the centre of a vast international mystery.

One day, April stumbles on a giant robot sculpture in Midtown Manhattan, and makes a video with the figure, which goes viral. She becomes famous as news spreads that similar sculptures have mysteriously appeared in dozens of cities, and people around the world struggle to understand where the figures came from and what they mean.

The novel, which will be published by Dutton in autumn 2018, flirts with otherworldly themes. But the story grew out of something very real Green has wrestled with in his own life: internet fame, and the anxiety and awkwardness it can bring.

"In a lot of ways it comes from a lot of my personal experience with how success feels," he said. "There's the very weird feeling of being bigger in people's heads than you feel you are."

To his legions of devoted YouTube fans, Green is best known as the goofy, enthusiastic host of factoid-heavy educational shows like SciShow and Crash Course, and as the younger half of "Vlogbrothers," the chatty video show that he created in 2007 with his older brother, best-selling novelist John Green. Over the past decade, the Green brothers have built an online video empire, with 16 shows that have collectively drawn more than 2 billion views on YouTube.

It may surprise Hank Green's YouTube followers to learn that he has been quietly writing fiction on the side. Even his brother John - who has published several young adult novels, including The Fault In Our Stars and Paper Towns - has yet to read a draft of the novel, Green said.

"It's very scary to think about him reading it, although I suppose he will soon," Green said. "I think of John Green my brother and John Green the author as different people," he added. "When I read a John Green book, I'm like, there's no way my idiot brother wrote this."

Green, 37, who lives in Missoula, Montana, with his wife and 10-month-old son, has been toying with the idea of writing a novel since he was in college. He started working on An Absolutely Remarkable Thing about six years ago, after having a strange dream that he realised had the elements of a mystery plot (the dream involved "a particularly weird death scene", Green said).

He first envisioned the book as a graphic novel, then realised that he had an outline for a novel that combined elements of science fiction and mystery. He carefully reread Frank Herbert's Dune while working on it, and read some of Michael Connelly's Harry Bosch detective novels to study how mystery novels are structured. To motivate himself to write, he set up a Patreon account, and online patrons paid him a dollar per chapter, and offered feedback. He also got advice from fantasy novelist Patrick Rothfuss.

Dutton, a Penguin Random House imprint, acquired the novel last month, as part of a two-book deal. An Absolutely Remarkable Thing, which Green says has vulgar language and adult themes, is written for adults. (John Green's young adult novels are published by Dutton Books for Young Readers.)

Green is perhaps more familiar with the publishing world than most debut authors. He's watched from the sidelines as John's literary career has taken off, thanks in large part to his YouTube fan base. This autumn, he'll join his brother on a book tour to promote John's highly anticipated new young adult novel, Turtles All The Way Down.

Still, Green is unnerved by the thought of his own book being widely read. Even for someone who is accustomed to exposure, and has bared so much of himself online, publishing a novel feels different, and strangely personal.

"Every character in the book is a different version of me," he said.