Max in the Land of Lies: A Tale of World War II (Operation Kinderspion)

Max Bretzfeld's dangerous mission begins when he returns home to Berlin as a British spy in the much-anticipated second book in Adam Gidwitz's duology that began with Max in the House of Spies.

Max was on a mission.
Well, two missions.
One mission his British spymasters knew about: infiltrating the Funkhaus, the center of Nazi radio and propaganda.
The other, they did not: finding his parents.

Max Bretzfeld was willing to do anything to return to Germany, even become a British spy. Training complete and forged papers in hand, the radio wunderkind’s mission has begun—gain access to the legendary Funkhaus, the base of operations for the Ministry of Propaganda and Popular Enlightenment headed by Joseph Goebbels.