Crystal Keepers: Five Kingdoms, Book 3

Book review by
Carrie R. Wheadon, Common Sense Media
Crystal Keepers: Five Kingdoms, Book 3 Book Poster Image
Exciting high-tech turn for the wordy series.

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Kids say

age 11+
Based on 2 reviews

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The parents' guide to what's in this book.

Educational Value

Unlike Elloweer and Sambria, the kingdoms from Books 1 and 2, Zeropolis is very modern. Readers can think about how this world of intelligent robots, high-tech battle suits, speedy trains, and power crystals compares with ours. They also can think about how much work it is for an author to create all the aspects of a new world from his or her imagination. 

Positive Messages

Good vs. evil is the central struggle for the whole series, and extreme bravery is required. As in Book 2, the abilities of tweens/teens (and one small robot here) are underestimated by the enemy -- always a mistake. There's also ample warning about what can happen when you let your AI get too smart and how free communication is the enemy of any dictator.

Positive Role Models & Representations

Cole's a very thoughtful and deliberate character who chooses loyalty to his friends over personal safety. He's decided that he's more comfortable in this world of danger now but still maintains a determination to get back to his own world, even after everyone else has lost hope.


There's a skirmish at the beginning outside modern Zeropolis where kids in animal form attack horses and people, and some guards die. After that, all the fighting is done in high-tech, nonlethal ways: nets that capture; foam and tar that harden over targets; some tranquilizer darts; and a drugging. When a monster rampages through the city, there's a mention that bodies are seen motionless on the sidewalk below. A bomb with no radiation detonates in an area outside where people live. Lots of talk of what might happen to Cole if he's caught spying -- he fears being tortured for information. A girl with half a prosthetic leg recalls the potential danger of pushing yourself too hard in battle suits that enhance physical abilities. Talk of a supercomputer that wiped out a whole city. Much talk of the loss of family in another world; when you cross over to the Outskirts, everyone you know forgets you ever existed.

Drinking, Drugs & Smoking

What parents need to know

Parents need to know that Crystal Keepers is the third book in the Five Kingdoms series from fantasy author Brandon Mull, who developed a big fan base from his Fablehaven and Beyonders series. If kids have already read some of Mull's books, they'll find this series less violent and just a little less complex than Beyonders. Unlike the first two books in the series, which include fantasy violence of the sword-and-arrow variety, only one skirmish at the beginning involves the killing of horses and guards that way. Then Cole and friends enter the modern city of Zeropolis and fight with high-tech, nonlethal weapons: nets that capture; foam and tar that harden over targets; and tranquilizer darts. Battle suits enhance physical abilities but can still harm the wearer -- a girl shows off her prosthetic leg as warning. Cole is always on the run from the bad guys and fears being caught and tortured for information. One robot causes a large explosion where people aren't hurt, and other takes out a few innocent bystanders.

User Reviews

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Teen, 13 years old Written byalphagirl2020 October 3, 2020

Can this world be real???? Please????!!

This is by far the best book in the series. No bad content, perfect for kids and even teens. I read this when I was nine, but I have a sixteen year old friend w... Continue reading
Teen, 14 years old Written byWyvernDC February 23, 2020

Fun and amazing .

Well for the people out there this was the first book I read(like the whole page) because we were force to write a book report. Even though i jump the Season of... Continue reading

What's the story?

Cole is on a princess-collecting mission. The high king who stole the powers of his five daughters is starting to weaken but is still a threat to them. Mira, daughter No. 5, found her sister Honor in Elloweer, freed her powers, and left her to train in safety with a special magician called a High Shaper. Constance is next on the list. She's hidden somewhere in the most modern kingdom in the Outskirts, Zeropolis. It's a place with robots, crystals that hold energy and information, and a more active underground movement called the Unseen to thwart the totalitarian tendencies of their High Shaper, who runs the city. They don't get past the train station before Cole's friend Joe is captured. Cole contacts the youngest members of the Unseen, the Crystal Keepers, and makes it to one of a network of hideouts in the city, explaining how important it is to find Joe. He has sensitive information about the princesses. He's barely explained the danger when the Enforcers close in, attacking that base and others in the city.

Is it any good?

If you're three books into the series, you know what to expect from Brandon Mull: His fantastic and complex worlds, not the storytelling, are the stars of the show. He's prone to really taking his time to getting the reader to the climax of the story, weaving in too much detail. In CRYSTAL KEEPERS, for example, there are so many levels of bad guy -- High King, High Shaper, a supercomputer, Owandell, Nazeem -- that we're carried off in too many directions.

It's fun to see Mull go from his sword-and-sandal epics to full-tilt sci-fi. Zeropolis, with its crystal energy, sophisticated AI, and fun tar guns and battle suits will make readers long for Mull to keep the rest of the series high-tech. Cole seems to be having a lot of fun with his battle suit, and Sidekick the robot will be hard to leave behind when he heads off to another world in Book 4.

Talk to your kids about ...

  • Families can talk about what the leader of the opposition says when talking about the head of Zeropolis: "Free communication is an enemy to control." Where in our world is this true? Think about how many countries restrict access to the Internet. Do the rulers of those countries have a right to do that?

  • Which is your favorite world in the Outskirts so far? Which hints do you have about the kingdom called Necronum from Book 4? If you were stuck in the Outskirts like Cole is, where would you like to live?

  • Will you keep reading this series? Have you read anything else from author Brandon Mull? What do you like about his writing?

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