The Mossheart's Promise (Hardcover)

The Mossheart's Promise By Rebecca Mix Cover Image
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From New York Times bestselling YA author Rebecca Mix comes the first book in a breathtaking middle grade fantasy duology about a young fairy who has always lived in her heroic grandmother’s shadow but now must step up and embark on a quest to save her mother from the ever-creeping mold overtaking their world.

Perfect for readers who loved Brandon Mull's Fablehaven, The City of Ember by Jeanne DuPrau, and Endling: The Last by Katherine Applegate.

The mold takes all.

Twelve-year-old fairy Canary Mossheart knows this better than most. A few years ago, the mold took her papa, and even her famous, former-chosen-one Gran never found a cure. So when Ary's beloved mama falls ill, Ary decides it’s taken enough. Armed with only a bucket and a prayer, she sneaks out to find a magical, underground lake whose healing waters are straight out of Gran’s adventures. 

But when Ary gets there, the lake’s bone dry, and instead of healing waters, she finds a terrifying secret: Her entire world is actually trapped inside a giant terrarium—one they were meant to leave centuries ago. Worse, Gran knew and hid the truthdooming Ary and her generation to a dying, rotting world.

Now, allied with only her doomsday-obsessed frenemy, a timid pill bug, and a particularly grumpy newt, Ary has one week to unravel the clues and find a way out of the terrarium—or they’ll be trapped for good. .

About the Author

REBECCA MIX is a New York Times and Indie bestselling author of stories about messy girls, eerie magic, and hope. She spent her childhood tromping through swamps and falling out of very tall trees—which, in hindsight, explains a lot. A reluctant reader at first, she fell in love with books after joining a reading contest to spite her fourth grade nemesis. Visit her online at

Praise For…

"An exciting, honest, and hopeful tale that speaks gently and clearly to kids’ fears and needs. It urges them to value their own experiences, reassures them that it’s OK to be angry when they’re left to pay for the mistakes of adults, and reminds them that kindness must guide us, even when we’re afraid. A wonderful story for all the scared people doing the right thing because nobody else will." — Kirkus Reviews (starred review)

"Boasting rich, confident worldbuilding and complex interspecies relations in a starkly rendered setting, this stirring middle grade debut from Mix (The Ones We Burn) passionately explores the courage it takes to lead with empathy and to become a hero in the face of older generations’ failures.” — Publishers Weekly (starred review)

“A tender, touching, and thrilling exploration of how we can save the future by challenging the past.” — Sofiya Pasternack, Sydney Taylor Honor Award-Winning author of Black Bird, Blue Road

"In this immersive middle grade fantasy debut, Rebecca Mix crafts a larger-than-life cast of ordinary heroes who grasp hope in the unlikeliest of times and places. A thought-provoking and unflinching reckoning of what it means to be the 'Chosen One' in a thankless, dying world -- where yet, still, love burns bright." — Katie Zhao, author of the Winnie Zeng series and The Dragon Warrior duology

Product Details
ISBN: 9780063254053
ISBN-10: 0063254050
Publisher: HarperCollins
Publication Date: September 5th, 2023
Pages: 432
Language: English