Eighteen-year-old Celaena Sardothien, aka the Assassin of Adarlan, knows her way around a sword. And, judging by the stellar sales and solid fandom of the books starring Celaena – the Throne of Glass series – author Sarah J. Maas knows her way around fantasy writing. The series’s first installment, Throne of Glass (Bloomsbury, 2012), marked Maas’s debut; it had evolved from a version of the story she wrote and posted online as a 16-year-old student. Now, with series sales topping one million units worldwide, and the series just optioned for television by the Mark Gordon Company (the studio behind Grey’s Anatomy, Showtime’s Ray Donovan, and the forthcoming Steve Jobs biopic), comes the fourth volume, Queen of Shadows, released September 1, along with a 10-city U.S. tour. Early enthusiasm for the title bumped Queen of Shadows to the #1 slot on PW’s September 14 children’s fiction bestseller list, as well as #5 on USA Today’s September 10 list of bestselling books, and Throne of Glass to #2 on the September 20 New York Times children’s series bestseller list.

Bloomsbury has beat the marketing drum for Maas’s series from the start, hitting the ground running with its marketing support of Throne of Glass back in spring 2012 when it released four prequel e-novellas set in the same world, priming readers for the novel’s fall 2012 publication. The hardcover became a regional bestseller out of the gate and that same season, Maas was selected as a PW Flying Start. When book two, Crown of Midnight, was released in 2013, it landed in the #5 spot on the New York Times’ young adult bestseller list and Heir of Fire (2014) debuted at #4 on the Times children’s series list. In the midst of Throne of Glass’s upward trajectory, Maas introduced the first book in a new trilogy, A Court of Thrones and Roses, which debuted on the Times young adult bestseller list at #2 this past May, and remained on the list for six weeks.

Bloomsbury editorial director Catherine Onder believes the books’ steadily rising popularity can be attributed to several factors including “her incredible characters, epic storytelling, and world filled with magic.” In Onder’s view, Celaena is “a fierce, anguished, and immensely powerful young woman who overcomes obstacle after obstacle to find herself and own her powers. Being a high fantasy heroine, of course she’s larger-than-life, but the core of her struggles is extremely relatable to readers. I think that’s a big part of the magic of this series – the sweeping scope and high stakes make readers feel on a grand scale, but we all experience these same emotions in our lives, and exploring them through this mirror of a new world feels transcendent.”

For Maas, watching her career take off has been “insane. Actually insane,” she says. “I’ve been writing this series since I was 16, and spent so many years daydreaming and working my butt off to make those dreams a reality that all of this is just beyond anything I could have hoped for. I don’t think I’ll ever stop being grateful to my readers for everything they’ve done for me.” Maas has come a long way from her initial, relatively modest, goal of seeing her book published one day. “My goals for myself have changed as my career has evolved and as I’ve grown as a writer,” she explains. “But I don’t think 16-year-old me would believe it if I told her that all of this incredible stuff has happened. I still don’t quite believe it.”

With fans eagerly awaiting more of Celaena’s adventures, Bloomsbury rolled out promotions for Queen of Shadows in mid-August, ramping up for the September 1 global on-sale date. On August 18, Maas participated in a Tumblr “AnswerTime” event and received more than 5000 questions in under an hour. Online advertisements promoted the first book, Throne of Glass, and were supported with a series read-along on social media (#ReadThroneofGlass) hosted by Bloomsbury. For the month of September, the read-along campaign shifts to the new book. Taking advantage of the simultaneous publication in its various territories, Bloomsbury began a #MapMyQueenofShadows campaign on September 1, inviting readers to share photos of their copy of the book along with their location. Bloomsbury will then add the photos to a Pinterest map showing readers from around the world. Director of Publicity Lizzy Mason reports that on launch day, “Readers from more than 90 cities in 18 countries, including the United States, England, Scotland, Australia, Canada, Spain, Israel, United Arab Emirates, Germany, Mexico, and Philippines, shared their excitement about Queen of Shadows and contributed to our map.” (see photos) Such groundwork has helped yield results, as Mason additionally notes that the laydown (total number of books printed, not just announced first-printing) for Queen of Shadows was a 100% increase over the laydown for Heir of Fire.

As Maas’s following has grown, the scope of her tours has changed somewhat as well. “Since my Crown of Midnight tour in 2013, we’ve had such a rapid jump in audience numbers that we’ve had to move to bigger venues, cap events, and find new and creative ways to keep the line flowing while still allowing me the chance to chat with each person, which will always be very, very important to me,” says the author. “But no matter the size or turnout, I think the events still remain fun, candid, and really positive.” She says that one new trend she’s noticed on the Queen of Shadows U.S. tour was that “we had a ton of readers who had never been to a book event before. It was such an honor to have them decide to try it out at one of the QOS tour stops, and so many of them left saying they couldn’t wait to attend another one!”

For her September tour, Maas has already visited Tempe, Salt Lake City, and Denver, among other cities, and will wrap up with two more stops: September 19 at the Costco in King of Prussia, Pa., and September 26 at a Costco in Brick, N.J. In November, Maas will tour Australia and New Zealand for the first time and will take part in the pop-culture expo Supanova. According to Mason, many of the events on the Australian leg sold out in a matter of hours.

Angela Mann, youth events manager at Kepler’s Books in Menlo Park, Calif., has hosted Maas several times for previous book tours. “Sarah J. Maas has a Kepler’s story,” says Mann. “We fell in love with her when she visited for Throne of Glass and welcomed her back for both Crown of Midnight and Heir of Fire. We’ve taken her on many school visits where she charmed large crowds of students and built huge fanbases. We watched our audience grow from 25 to 50, to 130 eager and enthusiastic fans.” Mann says that Throne of Glass has become one of her favorite series as well as many customers’ favorite. “And the series really has gone from strength to strength,” she adds, “full of action, so swoon-worthy, and just so addicting.”

Next up for Maas is the sequel to A Court of Thorns and Roses, due out in May 2016, and she says she is “just starting my editorial process” for the fifth installment in the Throne of Glass series, which is planned to end its run after six books. No doubt her supporters will be there in force as her oeuvre continues to expand. As Mann puts it, “We are forever fans.”