Their Will Undone

I recently learned about a new author, R.J. Valldeperas, whose books draw from her Peruvian and Venezuelan heritage. I’m currently in Lima, my husband’s home city, and have been craving more books set in and around Peru. I first heard of her upcoming adult fantasy… but then saw she also had a YA fantasy coming even sooner: Their Will Undone. It just came out last week and kicks off a duology inspired by the Inca empire.

Nina has just been chosen to be the emperor’s new bride, his second wife. The emperor sends Kasik to personally escort her to him. On their journey, Nina and Kasik start to form a close bond, but they also learn surprising truths about themselves along the way. By the time they’ve reached the emperor, they both have plans for what to do next… but it’s unclear how they can continue to be in each other’s lives afterwards.

What I Liked:

• Incan and Andean culture. Since meeting my husband, and especially since arriving in Peru, I’ve been curious to read more books set here and inspired by local history and culture. Their Will Undone fully delivers in this aspect. The book started from a real historical event over 500s years ago, the Children of Llullaillaco (in the Andes on the Chile-Argentina border). I love how the author weaves in the characters’ differing views on their shared history, the role of the gods, and what is possible in their present day.
• The chosen one, political unrest, and rebellion. The chosen one trope is common in fantasy, and not usually my favorite, but it’s done well here. Nina is just learning how to wield her power, but she has a long way to go still. I appreciate that, instead of finding the weight of the world on her shoulders, Nina’s goals remain focused on her family’s well-being. It feels more realistic. Nina and Kasik are both incredibly loyal, though sometimes they need to reevaluate who is deserving of that loyalty.
• Feminine rage and power. Nina and another character, the empress, show the beginnings of feminine power. Men may underestimate them, but they both have goals and the ability to achieve them. A lot is set up here for the second book.

What Didn’t Work for Me:

• It’s a lot to take in. This book introduces many themes and plot points, and it sometimes felt a bit too crowded. It could have benefited from some streamlining in the first half, or perhaps a longer page count. It settles more in the latter half, though, while leaving plenty of room to expand in the next book of the series.

Audiobook:

Elena Rey and Christian Barillas narrate as Nina and Kasik, respectively. Both do a great job in capturing their characters, including the pronunciation of words drawn from the Quechua language and other Andean names. This was an engrossing listen.

Final Thoughts

Their Will Undone is an absorbing fantasy perfect for anyone interested in Incan history and culture, political intrigue, and a forbidden romance. It has quite the ending, and I’m eager for the second book in this duology. While we wait for that, though, I’m also excited to read the author’s upcoming adult fantasy, Daughter of the Dark, out this September.

Special thanks to HarperCollins, HarperAudio Children’s, and NetGalley for providing me with an ARC of this book!

Get the Book

You can buy Their Will Undone here – it’s available as a hardcover, ebook, and audiobook.

Their Will Undone by R.J. Valldeperas
Series	Their Will Undone (#1)
Audiobook Narrator	Elena Rey; Christian Barillas
Audience	Young Adult
Genre	Fantasy
Setting	Peru
Number of Pages	368
Format I Read	Audiobook & Ebook (NetGalley ARCs)
Original Publication Date	June 2, 2026
Publisher	HarperCollins

Official Summary

A debut YA fantasy must-read for fans of The Winner’s Curse, What the River Knows, and This Woven Kingdom.

When a maiden is selected to marry the emperor, her journey to the palace will see her fighting both a spark of magical power and her growing feelings for her broody escort in this romantic fantasy duology opener, inspired by a true story from the Inca empire.

In Amaru, it is an honor to be chosen in the annual harvest and serve the gods’-favored emperor. Nina’s brother has already been chosen, but when the emperor’s men come a second time for her sister, Nina volunteers instead. She is taken to the acllahuasi, a gilded cage where women train to become servants or wives for the ruling class. It is there that a soldier comes to collect her, and Nina learns of her fate—to become a wife…to the emperor.

As the emperor’s trusted friend and soldier, Kasik is ordered to retrieve Nina and deliver her untouched. But the emperor’s betrothed is not as he expected. The distrust between Nina and Kasik is thicker than the trees surrounding them, and Kasik’s honor is put to the test when their path back to the capitol leads them into dangerous territory. Their lives and hearts are in peril as forbidden desires are unearthed, along with a stirring of dark magic in Nina that inexplicably ties her to the gods.

What begins as a simple task becomes a tense journey that forces Nina and Kasik to confront where their true loyalties lie—with the emperor and the fate of their people, or with the desires of their own hearts.

• Historical Inspiration: This story was inspired by the Inca Maiden of Llullaillaco.
• Betrothed’s Best Friend: When Nina arrives to the capital city, she’ll be married to the emperor of Amaru—who happens to be Kasik’s best friend.
• Forbidden Romance: Nina is engaged to the emperor. Kasik is a soldier in his army. Even so, they can’t deny the sparks that erupt between them.
• Forced Proximity: Nina and Kasik must work closely together to travel across the dangerous terrain leading to the capital.