(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

(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