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 center 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 fall 2018, flirts with otherworldly themes. But the story grew out of something very real Mr. 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, Mr. 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, the 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.