Millions of young adult readers across the country are besotted with John Green’s most recent novel, “The Fault in Our Stars.” When seen on Tumblr and Twitter, quotes from the book are usually followed by a string of distressed comments lamenting over the tragic story of John Green’s protagonists, two teenagers with terminal cancer.

One part young adult novelist, one part YouTube star, John Green has achieved a certain level of celebrity over the past few years that far outweighs that of most contemporary writers. In 2007, John Green and his younger brother Hank Green posted videos on their YouTube channel every day for a year. Their channel, Vlogbrothers, is still active today, with nearly 2 million subscribers.

In the early days of YouTube, an entire community called Nerdfighteria sprung up around the Vlogbrothers. This affectionate name for their fan base helps unify teenagers across the worldwide web. Their catch phrase, “DFTBA,” or “Don’t Forget to be Awesome,” is so well known that when President Barack Obama participated in a Google hangout with John Green last year, he was familiar with the term.

The brothers post videos on everything from giraffe sex to the current situation in Ukraine, speaking to each other and the Nerdfighter community, trying to educate and entertain. They interact with Nerdfighters on Tumblr and Twitter, creating a close-knit community through events such as VidCon, the largest convention devoted to online videos, and the Project for Awesome, a massive charity drive that collected over $800,000 last year.

Yet, John Green is significantly more famous than Hank Green. He has over 2 million Twitter followers, compared to his brother’s not quite 400,000. This difference can be attributed to John Green’s career as a novelist. His debut novel, “Looking for Alaska,” has long been a favorite among teens, climbing back into the New York Times best seller list seven years after its original publication in 2006. “The Fault in Our Stars,” which also spent weeks at the top of the list, has a movie adaptation coming out this summer.

While Hank Green’s career as a scientist and environmentalist is equally interesting, John Green’s books are more marketable and commercial.

John Green’s success as a novelist could be partially attributed to his massive online following, or perhaps many fans of his novels have stumbled on the Vlogbrothers after already being aware of the author. It is likely, though, that the two halves of his celebrity presence grew together, rather than one leading to the other.

John Green’s substantial online presence helps his books reach a wider audience and vice versa, proving that he is neither a novelist who makes videos nor a YouTube star who writes books, but a person who is highly successful as both a writer and a vlogger.

A version of this article appeared in the Thursday, April 10 print edition. Dylan Jarrett is books/theater editor. Email her at [email protected].