Unbreakable: The Spies Who Cracked the Nazis’ Secret Code
by Rebecca E. F. Barone
Intermediate, Middle School    Holt    272 pp.
10/22    9781250814203    $19.99
e-book ed.  9781250814210    $10.99

Barone (Race to the Bottom of the Earth, rev. 5/21) delivers another impressive feat of narrative nonfiction storytelling. In the years following World War I, Germany developed a virtually unbreakable code, called Enigma, with the help of a complicated machine. One such machine fortuitously fell into the hands of Poland, enabling their ­codebreakers to duplicate the machine and crack the code—until the Germans added layers of complexity. As Hitler rose to power, the threat of military aggression became obvious, increasing the stakes substantially; the code was central to military operations, particularly the German naval strategy. France, England, and Poland now had extra motivation to cooperate with one another to break the code; and break it they did, but not before an extensive game of ­cat-and-mouse with Germany. ­Accompanied by occasional ­black-and-white ­photos, Barone’s suspenseful text introduces a sprawling cast of characters, with the epilogue updating readers on what happened afterward to the central ­players. A timeline, bibliography, and source notes are appended.

From the March/April 2023 issue of The Horn Book Magazine.