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 a monthly installment about Magnus Bane, a character from Clare's Mortal Instruments saga. Ten e-singles are planned.

Despite her popularity online and in the U.K., Johnson has a relatively low...