Shannon Messenger takes a detour in Unraveled, book 9.5 in her bestselling Keeper of the Lost Cities middle grade series. The first book to be narrated from an entirely new POV and the second .5 installment following Unlocked (book 8.5), Unraveled centers on elven teenager Keefe Sencen after he split off from Sophie Foster in Stellarlune. What did Keefe get up to while he was traipsing through Humanland? What mysteries did he uncover and what secrets did he learn? In a conversation with PW, Messenger reflected on writing from a different perspective, the evolution of the series, and her goals for the future.

How do Unlocked and Unraveled fit into the overall series timeline?

My editor [Kara Sargent] and I had a lot of debates about what we should call these. We decided to go with the .5 in the title to try to make it clear where in the chronology you should read them. Unlocked is 8.5 because you need to read it after book eight [Legacy], otherwise it will have some spoilers in it. But you also need to read it before book nine, because it clarifies certain things in Stellarlune.

“This series continues to take me by surprise.”

Unraveled is very much the same: it’s covering the gap in book nine where Keefe is gone—a period of time that is happening simultaneously with Stellarlune. In this book, we get to find out what he was doing, so you absolutely need to read it after book nine. Otherwise, it has a ton of things that will spoil Stellarlune for you. But you also need to read it before book 10 for a lot of the revelations that are going to happen in that book to make sense.

Did writing from a new perspective in this universe present any unique challenges?

Absolutely. In this case, especially because the system was reversed—I was writing about an elf character in the human world instead of a character who grew up human suddenly in the elf world. It’s one of those things where you get so comfortable writing in one voice that, when you switch, you have to really think about how something would be said and what their worldview would be. What kinds of similes and metaphors would Keefe use? I had to make sure I was channeling his worldview into his adventures and that he wasn’t using human slogans and didn’t come off as being too familiar with everything.

Do you anticipate adding more books to the series that follow other characters’ perspectives?

This series continues to take me by surprise, in part because I’ve never written a series this long before. I just try to trust the story itself. At this point, I have absolutely no idea what curveball it’ll throw at me. I always try to find a solution to those surprises that doesn’t require doing another interstitial book but sometimes I have to roll with it. There are some huge things that are going to happen to some other characters, so it’s possible that I might need to write other stories—even if it’s not necessarily another entire book—to work through them. I won’t really know until I get there.

I feel like I’ve spent the first half of the series raising a ton of questions and introducing these characters that readers have gotten very attached to, and now that I’m winding it down, I owe readers answers, and I owe those characters the completion of their journeys. I want to make sure that we end the series on a high note. I remember at one point a few years ago I was starting to plot the ending, and I posted a tweet asking about long-running book or TV series endings that everyone was really happy with. The list was shockingly short. So now I’m staring down a very daunting task, but I’m up for it. That’s why I’m willing to pivot and do things like write book 9.5: I’m going to go with whatever the story demands I do in order to give that satisfaction, no matter how many weird detours we have to use to get there.

What can you share about the yet-to-be-announced 10th book in the series?

There are some really big secrets that Keefe is keeping, and secrets have a way of coming out. Anything that Keefe is choosing to hide at the end of Unraveled is not necessarily going to stay hidden, and it’s going to play a key role.

When I started outlining book 10, I realized that I needed to find a way of working Unraveled in. Originally, I thought, “As soon as he gets back, he’ll just tell everyone what he was up to, and we’ll be able to keep moving.” But it didn’t make sense from how he was feeling at the time and even if it did, that scene would just be like, “Sit down and let me tell you about this stuff.” And not having readers go on that journey with Keefe was making those scenes where his secrets come out very hostile. Now even though the characters are feeling betrayed and are obviously still in the dark, readers won’t be because they’re coming in with that prior knowledge. It gives the book an entirely different tone.

How has the series evolved over the last decade?

I was lucky that I got a three-book deal. I remember sitting my agent [Laura Rennert] down and saying, “This series is going to be more than three books. What do I do?” She said I needed to find a way to shape what we had into three books because the reality of a debut author getting to write 10 books in the same world is a long shot in publishing. It’s not impossible, but I needed to try and be realistic. If three was all I was going to get, I had to make sure it was a satisfying three. The fact that I’m still getting to tell this story makes me want to sit back and marvel at what it’s become.

I always say that Keeper launched into the world with a whisper, not a shout. It was something that grew organically: from booksellers handselling it, and teachers and librarians getting behind it, and readers telling their friends to read it so they could talk about it. Then the series hit the New York Times bestseller list, and it just kept growing from there. I’m so grateful that I’m getting to tell this story the way it always needed to be told, even if we’ve had to change up some of my original plans to fit within the realities of publishing. In many ways, that made it better.

Keeper of the Lost Cities: The Graphic Novel Part 1 was released last year, and earlier this year, Warner Bros. acquired film rights to the series. Do you have any updates regarding the future of Keeper of the Lost Cities?

I’ve seen some very rough preliminary sketches of part two of the graphic novel, but I’m set to start seeing the actual panels in the next couple of months.

As far as the movie goes, it’s so hard to know with Hollywood because you’re not allowed to say much. But I will say that the team we have on board right now is a powerful, completely dedicated team—the producer that’s behind it, and even the head executives at Warner Bros. are very passionate about bringing Keeper into the world and getting it done right. All we can really do is cross our fingers and hope for the best.

What’s next for you?

In 2016, I sold a standalone middle grade novel that’s still sitting on my laptop along with the revision letter from my editor, waiting for me to have time to revise it. It actually sold about two months before the Keeper series hit the bestseller list. Suddenly, everyone was like, “That one can wait. We want you to focus on the next book in the Keeper series. As soon as it’s done, you can revise that one.” But then we had to go straight into the next book. And so here we are.

I’m looking forward to being able to go back to that standalone novel at some point. I have quite a few other ideas percolating, but my brain is still very much in the Keeper world, so it’s hard to decide which one of those will be next.

Unraveled (Keeper of the Lost Cities #9.5) by Shannon Messenger. Aladdin, $21.99 Dec. 3 ISBN 978-1-6659-6741-9