BookTok sensation Alex Aster stepped away from the worlds of her bestselling “Lightlark” and “Starside” novels this week to celebrate the debut of her new book, which is based on IP that predates her works by more than six decades: Barbie.

Author Aster, who has now released 10 titles over the past six years, was brought on by Mattel to write “Barbie Dreamscape,” the first-ever YA series based on the beloved doll. And Aster says she was given creative freedom to do what she wanted with everyone’s favorite pick icon from the start, including deciding what other members of Barbie’s world to include.

“Obviously, Barbie was always going to be the main character,” Aster told Variety during an interview at Tuesday’s “Barbie Dreamscape” release-day party at the Barnes & Noble Bookstore in Union Square, New York. “I wanted Ken to make an appearance, but I didn’t want it to be all about Ken because this is first and foremost a journey of self-discovery for Barbie, and I didn’t want her to have to prove her strength based on a relationship and so that’s why she’s alone. Like, she sees a lot of people, she meets people during her quest, but ultimately it’s up to her to find her own strength and find her own destiny. So it was important to me that none of the secondary characters were stronger than her or were going through the entire journey with her.”

From Mattel Press, “Barbie Dreamscape” is described as “a richly imagined coming-of-age story about teenage Barbie, whose perfectly planned future is shattered when she is declared Fateless at her enchanted school’s graduation. To earn a Fate, she must journey across treacherous, magical lands in search of the mysterious beings who control the destinies of everyone in Heartland — and the buried truths that could change her world forever.”

Aster says she wanted this book to include new characters as well, “so all of the magical people she meets during the quest across the worlds, I wanted to create them to be inspired not only by Barbie products, but by the animated movies and just how Barbie made me feel.”

“When I went to Mattel, they let me play with the toys and see everything,” Aster says. “So it was a mix between me wanting to add something new to this one story and Barbie’s many lives, but also honor the Barbie I knew from movies.”

Aster, who says her favorite animated Barbie movie is 2001’s “Barbie in the Nutcracker,” could see the “Dreamscape” story being easily adapted into another cartoon by Mattel or potentially the first live-action YA “Barbie” film.

“I think it would be a really great animated movie. I love Barbie animated movies. I think Mattel could make an amazing adaptation, and that would be great to get to see it,” Aster says, adding: “If it wasn’t animated, if it was live-action, I would love to know what readers would want as a fan cast for a YA Barbie.”

Who would Aster want?

“I honestly don’t know,” the author says. “I tried to think about it but I also feel like readers are always so much better at that than authors are because we’re busy writing the books. But sometimes I’ll go online, I’ll be tagged [in a fan-cast post] and it’s like, ‘Fantastic! You guys should work for Hollywood. You guys are amazing.’ They’re great readers. And readers have a lot of power, too. For my other adaptations, I send a lot of that to the producers. I’m like, ‘This is what they’re saying. Listen to them; they’re really smart.’ But I don’t have [a fan cast for Barbie], but I’m sure someone will come up with the perfect one.”

Aster says she takes fan-casting quite seriously, and has been keeping her eye on readers’ comments about the upcoming film adaptations of her books “Lightlark” (set up at Universal Pictures and Temple Hill) and “Summer in the City” (New Line Cinema). But apart from flagging fans’ preferred actors and reviewing scripts, she’s taking a more relaxed approach to her executive producer roles on both projects.

“I’m definitely fully, totally focused on writing books, so I do not have plans on self-adapting,” Aster says. “There are amazing screenwriters who are working on the scripts. I’ve read the ‘Lightlark’ script; it’s really good. So they are so good at what they do, and I’m involved as an executive producer. I’m really lucky that these studios and producers value my feedback, and I think they understand how important readers are. And I’m lucky enough to have a good connection with my readers. So I’ve been really happy so far, but I think it’s either one way or the other: either I focus fully on the books or fully on the scripts or adaptation, and I’ve chosen the books for now. But everything’s really good and all you can ask for is that people love the work as much as you and your readers do, and they’re so talented, and they’ve done such a good job. So I’m really happy at this point with everything.”

When it comes to her day job, Aster has completed work on her next “Starside” book, “Stormside,” which was delayed from its Nov. 17 release date and is currently eyeing an early 2027 launch. Aster says the marathon writing journey for that book took a toll on her she’s still recovering from as she launches “Barbie Dreamscape.”

“I am done with ‘Stormside,’ the second ‘Starside’ book. It’s the longest book I’ve ever written,” Aster says. “It’s over 1,000 pages on my laptop. It has taken years off my life span. But every book is a new challenge. [‘Barbie Dreamscape’] was a new challenge. Even just working within the confines of an IP really, weirdly, felt more freeing. When you have these characters that you’re building in this world that is so well loved, I did just feel like anything was possible, so I really loved working within the IP.”

Aster says the experience was such a good one that she would even be open to writing another Barbie book.

“I would love to. If Mattel wants me to, I will,” Aster says. “But I think that this is just one of probably hundreds of Barbie stories out there, and so I’m just really grateful to have made a little piece of Barbie’s world.”