12 Apr Book Review: 39 Clues Book Series by Rick Riordan (and various authors)

The 39 Clues series is one of those ambitious, multi-author projects that manages to pull together history, mystery, action, and family drama in a way that feels genuinely exciting for middle-grade readers (and, honestly, a bit addictive for adults too). The whole thing spans multiple books and spin-offs, with different authors taking turns at the helm, but it all starts with a simple, thrilling premise: two kids get pulled into a globe-trotting hunt for clues that could lead to unimaginable power.

What’s it about?

The series kicks off with The Maze of Bones by Rick Riordan and follows siblings Amy and Dan Cahill. After the death of their grandmother Grace, the children—along with a collection of strange and colorful extended family members—are summoned to the reading of her will. But this isn’t just a typical inheritance moment. Instead of money or property, Grace offers her heirs a choice: take a million dollars and walk away, or accept the first clue in a hunt that could lead to the greatest secret the world has ever known.

Amy, a bookish 14-year-old, and Dan, an 11-year-old with a photographic memory and a bit of a wild streak, choose the clue.

From there, they’re plunged into a centuries-old conflict that ties their family to nearly every major figure in history—from Napoleon to Benjamin Franklin, from Mozart to Amelia Earhart. The Cahill family, it turns out, is divided into different branches, each with its own strengths, secrets, and strategies. And not all of them are playing fair.

As Amy and Dan chase clues across continents, they find themselves constantly outwitting, outrunning, and occasionally teaming up with various cousins and rivals. There are puzzles to solve, artifacts to find, and codes to crack. Each book in the series focuses on a different location and historical figure, which gives the whole thing an Indiana Jones-meets-National Treasure kind of feel.

The hunt leads them everywhere: underground tombs, ancient libraries, stormy seas, hidden chambers, and more. Along the way, they begin to piece together the truth about the 39 clues, which when combined, form a serum that could make someone the most powerful person on Earth. But of course, power like that comes with a cost, and as the series progresses, Amy and Dan are forced to ask bigger questions—not just about who they can trust, but about what kind of people they want to become.

The original series includes 11 books, each written by a different author (including Gordon Korman, Jude Watson, and Peter Lerangis), and it expands into several companion series like Cahills vs. Vespers and Unstoppable. But the heart of it always comes back to Amy and Dan and their journey from ordinary kids to globe-trotting adventurers.

What This Chick Thinks

A genuinely fun blend of education and action

One of the best things about this series is how it weaves history into the story without ever feeling like homework. You learn about everything from classical music to ancient artifacts to secret societies, but it’s all embedded in fast-paced action. The stakes are always high, and the historical figures are presented not as dusty facts but as vibrant pieces of a much larger puzzle.

For a younger audience, it’s the kind of thing that can spark real interest in history. For older readers, it’s just plain clever.

Amy and Dan are easy to root for

Amy and Dan are great protagonists because they’re both smart in different ways and constantly growing. Amy is cautious and introspective, while Dan is impulsive and daring. Their sibling dynamic feels authentic—they bicker, they support each other, they make mistakes, and they learn. You genuinely want them to win, not just because they’re the heroes, but because they feel like real kids trying to do the right thing in a world full of secrets.

Their development across the series is one of the most rewarding parts. They go from being overwhelmed and unsure to brave and resourceful, but they never stop being kids. That balance keeps the story grounded even as it gets more complex.

Some unevenness, but the momentum carries it

Because the series is written by multiple authors, there are definitely shifts in tone and pacing from book to book. Some installments are stronger than others—more emotionally resonant or tightly plotted—but the central mystery and the character arcs keep everything moving forward.

The continuity is pretty impressive, considering the rotating authorship. Each book builds on the last while introducing new layers to the mystery and new corners of the Cahill family tree.

A gateway to bigger themes

Beyond the action and adventure, the series digs into some weightier ideas: the corrupting nature of power, the importance of loyalty, and the dangers of obsession. Amy and Dan aren’t just solving puzzles—they’re navigating grief, identity, and moral dilemmas. And while the books never get too heavy, there’s definitely more going on under the surface than you might expect from a kids’ series.

Final Thoughts

The 39 Clues series is smart, fast-paced, and packed with just the right blend of danger, brainpower, and heart. Whether you’re twelve or thirty-two, there’s something satisfying about watching two ordinary kids hold their own in a world full of secrets and ambition. It’s a sprawling, twisty ride, and once you start, it’s hard not to keep going.

Rating: 8/10

Try it if you like

• The Mysterious Benedict Society by Trenton Lee Stewart – Smart kids solving puzzles with big-picture consequences and a great sense of humor.
• Alex Rider by Anthony Horowitz – For more globe-trotting action with a young protagonist and a dash of espionage.
• National Treasure (movie series) – If you like history-themed treasure hunts with plenty of twists and adventure.