Maureen Johnson has had a very good decade. In the 10 years before she turned 40 this month, Johnson published 10 YA novels, collaborated with John Green and Lauren Myracle on an 11th, contributed to several anthologies, wrote the screenplay for a Harry Potter video game, and was named one of Time magazine’s top people to follow on Twitter (she has nearly 73,000 followers).

She also ascended to the throne: Johnson recently bested nine other writers to win the U.K.’s Queen of Teen award, a two-year title whose recipient is chosen via online voting. That prompted a tweet, of course: “Being Queen: The Beginner’s Guide. 1. Get a castle 2. Build drawbridge to castle 3. Include moat 4. GUARD DOGS (Corgis).”

Johnson can’t rest on her laurels. Book two in her paranormal Shades of London series, The Madness Underneath, will send her on tour this spring, and she’s collaborating with Cassandra Clare and Sarah Rees Brennan on a digital serial, The Bane Chronicles. Beginning in April, the trio will produce an installment each month about Magnus Bane, a character from Clare’s Mortal Instruments saga. (A film based on the Mortal Instruments series, City of Bones, will be released in August.) Ten e-singles are planned.

Despite her popularity online and in the U.K., Johnson has a relatively low profile—compared to the company she keeps. Clare is a pal; so, too, is Green, a writing buddy for a decade. Johnson has appeared as his “secret sister” on the vlog he produces with his brother Hank, though she admits even she has felt occasionally overwhelmed by Green’s omnipresence.

“I was in England on the phone with my mom who tells me, ‘Oh, my book club is reading a book by that fellow you know. The Fault in Our Stars?’ And I’m like, ‘Of course you are,’ ” Johnson says. “And then I turned around and there he was on my TV! I had the BBC Breakfast on and they were interviewing him. I was fairly certain I’d pull back the shower curtain and find him there, too.”

Though Johnson is quick to credit Green with being first among peers to see the potential in social media (“We laughed at him. We were like, ‘When are you going to have time to do that?’ ”), she also qualifies as an early adopter. “I got into the business at the beginning of the first YA boom,” Johnson says. “There had been this idea of the writer in his apartment, drunk from morning to night, who produced a story while somebody else did all the other stuff. Suddenly you had to run the whole farm: handle the mail, be online, appear on a panel, and, yes, also write the book.”

Johnson developed into an able farmhand, taking on more than was probably required. A musing in a tweet would turn into a fundraising campaign for a worthy cause. She spearheaded YA for Obama, and encouraged followers to BEDA (Blog Every Day in April), even when she got too busy to do so herself. Two years ago, she took on organizing the literary track at LeakyCon, a conference for Harry Potter fans. She gets the “When do you have time to write books?” question frequently. “When I worked in theater I was always writing things on post-it notes and sticking them on screens or desks,” she says. “Twitter has given me a way of continuing to post those notes, only a lot of other people see them, too.”

And as a trailblazer, she also feels compelled to correct some of the misinformation she regularly hears about the “right way” to use social media. “I’ve heard people on panels say, ‘You MUST have a Web site. You need to tweet. Repeat the title of your book constantly, and I just want to say, ‘Shut up. Everything you’re saying is wrong,’ ” Johnson says. “People will know instantly if your only motivation for tweeting is to sell books. My rule is: the second you find yourself doing something you hate, quit doing it.”

Johnson came to write YA novels via an unconventional route. She and her agent, Kate Testerman, met at University of Delaware. After graduation, they settled in as roommates in New York. Testerman became an assistant at Janklow & Nesbit Associates. Johnson enrolled at Columbia University for an M.F.A. in dramaturgy, but grew tired of “divas and the ridiculousness” and switched to writing.

“What broke me finally was working with a famous, but unbearable, director who would say, ‘I hate story! This play will have no story!’ and do things to cause the audience actual pain, like refuse to muffle gunshots so when the gun went off, it was so loud the police kept coming to the theater,” Johnson recalls. “The people in charge had been in theater for 30 years and won all the awards and they were just crazy. They’d say, ‘Everybody take off your pants,’ and everybody would!”

Then came a fateful meeting Testerman had with 17th Street Productions (now Alloy Entertainment). “They showed me samples of the kind of writing they were looking for,” Testerman said. “I immediately thought of Maureen. She had a voice that was perfectly in tune with teenagers.”

Johnson wound up writing five novels under her own name packaged by 17th Street Productions: The Key to the Golden Firebird, Girl at Sea, 13 Little Blue Envelopes, The Bermudez Triangle and Devilish, cementing a reputation as a writer who delivered more than required.. “She overachieved,” Testerman said. “She was able not only to capture what they were looking for but to also make it her own.”

The idea for Shades of London began while Johnson was doing research for a sequel to 13 Little Blue Envelopes. During a tour of Parliament, she was struck by how many times the guide mentioned that such-and-such place was reputedly haunted. “I suddenly wondered, ‘Why have I never written a mystery?’ I read two mysteries a day when I was a kid. All of Agatha Christie, all of Sherlock Holmes. I’ve seen every single British detective show ever made. I had to do it.”

Book one, The Name of the Star, was nominated for an Edgar Award; The Madness Underneath comes out February 26. Penguin is repackaging her early Razorbill titles – Devilish and The Bermudez Triangle (which has been retitled On the Count of Three) and Testerman recently sold six of Johnson’s backlist titles to Hot Key Books in the U.K., hoping to capitalize on her two-year reign. The Queen of Teen is ready for her second act, it seems.