(3) 4-6 39 Clues: Doublecross series. As the Cahills crisscross the world searching for clues that will stop the Outcast from re-creating the fourth and final historical disaster (a Chernobyl-like nuclear meltdown), siblings Amy and Dan discover the true extent of the disgraced former Cahill's revenge plot: to wipe out the Cahill bloodline forever. This final volume is packed with close calls, suspense, and surprises.

Reviewer: Lana Barnes

(3) 4-6 39 Clues: Doublecross series. In their third mission, the Cahills divide and conquer: while one team travels to the Netherlands to stop the Outcast's next disaster--an event projected to rival Hurricane Katrina--a second looks to history for clues to stop the Outcast indefinitely. This nail-biter packs historical and cultural facts in with suspense and mystery for a generous portion of action-adventure with a side of knowledge.

Reviewer: Lana Barnes

(3) 4-6 39 Clues: Superspecial series. The CIA hires the Cahills to find their estranged cousin Sinead Starling, who has stolen incurable virus samples from the U.S. government. To prevent a global health crisis, Amy and Dan travel to Cuba and the Bermuda Triangle. This new spinoff is more tightly focused than its precursors but has the same high stakes and fast-paced action fans have come to expect.

Reviewer: Lana Barnes

(4) 4-6 39 Clues: Doublecross series. The Outcast, a vengeful former Cahill, continues to challenge the young Cahills by re-creating famous world disasters that they must stop, here the Hindenburg explosion. The smart, quick-thinking crew is led to a passenger airship competition where they must figure out which vessel is targeted before time runs out. Forced plotting makes this spinoff-series entry one of the weaker ones.

Reviewer: Lana Barnes

(3) 4-6 39 Clues: Doublecross series. As the newest leader of the Cahills, seventeen-year-old Ian Kabra must prevent the re-creation of four historical disasters to prove himself worthy to the Outcast, a vengeful former Cahill. Ian and his crew race to avoid any more blood on the family's hands. Suspense and tension are at the center of nearly every scene in this spinoff series' plot-focused, unpredictable opener.

Reviewer: Lana Barnes

(4) 4-6 39 Clues: Unstoppable series. Cahill siblings Amy and Dan continue their dangerous mission to stop evil media mogul Pierce from world domination in the spinoff series' second and third books. Relationships are tested and loyalties questioned when Amy takes matters into her own hands in Breakaway and makes a rash decision in Countdown. Plot development feels a little sluggish, but action-heavy moments raise the stakes. Review covers these 39 Clues: Unstoppable titles: Breakaway and Countdown.

Reviewer: Lana Barnes

(3) 4-6 39 Clues: Unstoppable series. In the strong finale of this 39 Clues series spinoff, siblings Dan and Amy race to produce the antidote to the Cahill serum before media tycoon J. Rutherford Pierce sets his world-domination plan into action. Korman puts the series back on its tracks with swift plotting and unexpected twists.

Reviewer: Lana Barnes

(4) 4-6 39 Clues: Unstoppable series. Cahill siblings Amy and Dan continue their dangerous mission to stop evil media mogul Pierce from world domination in the spinoff series' second and third books. Relationships are tested and loyalties questioned when Amy takes matters into her own hands in Breakaway and makes a rash decision in Countdown. Plot development feels a little sluggish, but action-heavy moments raise the stakes. Review covers these 39 Clues: Unstoppable titles: Breakaway and Countdown.

Reviewer: Lana Barnes

(3) 4-6 39 Clues: Cahills vs. Vespers series. Siblings Amy and Dan reach a breaking point when they discover the Vespers' fatal plan (Trust). In Doom, the two face the near-impossible task of destroying a Doomsday device and shutting down the Vespers indefinitely. The final two entries in this suspenseful series are more focused and deliberately paced than previous books, which helps bring the story to a satisfying conclusion. Review covers these 39 Clues: Cahills vs. Vespers titles: Day of Doom and Trust No One.

Reviewer: Lana Barnes

(3) 4-6 39 Clues: The Cahill Files series. More Cahill history is unlocked in this second collection of one-off stories. This book focuses on three teens: Frederick Warren in 1814 Maryland, Harry Houdini in 1891 NYC, and Fiske Cahill in 1955 Connecticut, each of whom battle Vespers to protect Gideon's ring, a Cahill treasure. The well-explored historical backdrops provide context for these adventures, rooting the reader in each time and place.

Reviewer: Lana Barnes

(4) 4-6 39 Clues: Unstoppable series. Six months after sixteen-year-old Amy and thirteen-year-old Dan defeated the Vespers, the Cahill siblings set out on another quest to stop the serum their family has protected for centuries from wreaking havoc on the world. This first entry in a new spinoff series is formulaic, but the suspense and high stakes that 39 Clues fans love are front and center.

Reviewer: Lana Barnes

(4) 4-6 39 Clues: Cahills vs. Vespers series. Eager to save their kidnapped family members, siblings Dan (thirteen) and Amy (sixteen), continue to take orders from their enemy, Vesper One. Crisscrossing the world, the Cahills search for ancient artifacts, while dodging Interpol and the conniving Wyoming siblings from the clue hunt. The high-stakes (if formulaic) plot moves quickly and builds suspense, while historical facts are woven into the stories. Review covers these 39 Clues: Cahills vs. Vespers titles: The Dead of Night and A King's Ransom.

Reviewer: Lana Barnes

(3) 4-6 39 Clues: Cahills vs. Vespers series. Siblings Amy and Dan reach a breaking point when they discover the Vespers' fatal plan (Trust). In Doom, the two face the near-impossible task of destroying a Doomsday device and shutting down the Vespers indefinitely. The final two entries in this suspenseful series are more focused and deliberately paced than previous books, which helps bring the story to a satisfying conclusion. Review covers these 39 Clues: Cahills vs. Vespers titles: Day of Doom and Trust No One.

Reviewer: Lana Barnes

(3) 4-6 39 Clues: The Cahill Files series. In this spin-off series, readers are made privy to Cahill family secrets. This story relates the family's involvement with Van Eyck's altar piece--a set of twenty-four paintings--through three generations, beginning in the sixteenth century, to World War II, and finally to the present day. Riley uses vivid language to create a narrative that series fans will enjoy.

Reviewer: Lana Barnes

(4) 4-6 39 Clues: Cahills vs. Vespers series. In this fourth installment of the interactive series, siblings Amy, sixteen, and Dan, thirteen, continue to track down priceless treasures to ensure the safety of their family members being held hostage by the Vespers. The stakes are raised when one of the hostages is separated from the pack, but multiple side stories and characters cause the plot to lose focus.

Reviewer: Lana Barnes

(3) 4-6 39 Clues: Cahills vs. Vespers series. Vesper One, a centuries-old adversary, kidnaps seven members of the powerful Cahill family. Thirteen-year-old Dan and sixteen-year-old Amy, winners of the clue hunt from the first 39 Clues series, must steal a national treasure and deliver it to the Vespers in exchange for the hostages. The fast-paced, action-packed adventure gets this spin-off series started with a bang.

Reviewer: Lana Barnes

(3) 4-6 39 Clues series. Also written by Jude Watson. In four engaging short stories (each written by a different author), origins of the five-hundred-year-old animosity between the Cahills and the Vespers are explained. The volume ends in modern times, with Amy and Dan continuing to gather clues to locate the ring and keep it hidden from Vespers. Though the kids' original 39 Clues adventures have ended, this book seems to indicate another series.

Reviewer: David Elzey

(4) 4-6 39 Clues: Cahills vs. Vespers series. Eager to save their kidnapped family members, siblings Dan (thirteen) and Amy (sixteen), continue to take orders from their enemy, Vesper One. Crisscrossing the world, the Cahills search for ancient artifacts, while dodging Interpol and the conniving Wyoming siblings from the clue hunt. The high-stakes (if formulaic) plot moves quickly and builds suspense, while historical facts are woven into the stories. Review covers these 39 Clues: Cahills vs. Vespers titles: The Dead of Night and A King's Ransom.

Reviewer: Lana Barnes

(3) 4-6 39 Clues series. At the conclusion of the ten-book worldwide treasure hunt, can Amy and Dan Cahill solve the clues leading to their aunt's fortune? While the series has utilized gimmicky collectible cards and interactive online clues throughout, it is the story, with its focus on civility and family unity, that triumphs. Short chapters and nonstop action compel readers to the very end.

Reviewer: David Elzey

(4) 4-6 39 Clues series. In Nest, Amy and Dan learn some unpleasant truths about their family's lineage while trying to evade the Holts in South Africa (among other places). Code finds the sibs dramatically separated in China. Warning takes them to the Caribbean--and a showdown with the man in black. The series continues to spit out compulsively readable, if slight, tales of adventure. Review covers these 39 Clues titles: The Emperor's Code, The Viper's Nest, and Storm Warning.

Reviewer: Elissa Gershowitz