Keys to the Demon Prison
by Brandon Mull
Random House 2026
Easy read — content targets 6th grade and up
Reading level 5.6 (5th grade) but themes aimed at ages 11+
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Genre
Themes
- courage
- sacrifice
- good vs. evil
- family and sibling bonds
- trust and loyalty
- responsibility and leadership
- temptation and choices
- teamwork
About this book
In the epic finale of the Fablehaven series, siblings Kendra and Seth race to stop a plan that could unleash an army of demons into the world. Their quest leads them across magical preserves, testing their courage, trust, and ingenuity as powerful enemies close in. Packed with nonstop action, clever puzzles, and wondrous creatures, this conclusion thrills fantasy fans. Great for strong middle-grade readers who enjoy high stakes, teamwork, and richly imagined worlds.
Setting: contemporary world and secret magical preserves worldwide, culminating at the demon prison Zzyzx
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Frequently Asked Questions
Is Keys to the Demon Prison right for my child?
It depends — here's what to consider for Keys to the Demon Prison. The reading level is AR 5.6, which is typical for 5th grade. The interest level is rated Middle Grades Plus (6+), meaning the themes and content are designed for ages 11+ (6th grade and up). Themes include courage, sacrifice, good vs. evil.
How long does it take to read Keys to the Demon Prison?
At a typical 5th grade reading pace, Keys to the Demon Prison takes around 14h to finish. The book has 141,000 words. Slower or faster readers may vary significantly.
Does Keys to the Demon Prison have an AR quiz?
Yes — Keys to the Demon Prison has an AR quiz available, worth 19 points. Your child will need to take and pass the quiz through their school's Accelerated Reader program to earn credit. The quiz is typically 5–20 multiple choice questions about plot, characters, and setting.
What grade level is Keys to the Demon Prison?
Keys to the Demon Prison has an AR reading level of 5.6, which places it at a 5th grade reading difficulty. The interest level is rated Middle Grades Plus (6+) — this reflects the age-appropriateness of the content and themes, not just the reading difficulty. A strong younger reader may handle the words fine while the themes are aimed at an older audience, or vice versa.