Since 1933, the Hitler regime had forced nearly half a million people into exile. The stream of refugees grew with every new aggressive act of foreign policy on Hitler's part. Erika Mann solicited monetary donations and organised entry visas and residence permits for emigrants from Austria, Czechoslovakia, Spain and – starting in 1940 – from occupied France. Before emigrating, she had “only” written for the newspapers and for children. Exile turned Erika Mann into a writer of books. In 1938, her political exposé Zehn Millionen Kinder. Die Erziehung der Jugend im Dritten Reich [School for Barbarians. Education under the Nazis] was published in German and English. The book became a bestseller; 40,000 copies were sold within three months of the English edition being published. With “The Lights Go Down”, a collection of stories published in 1940, Erika Mann provided insights into everyday life in the Third Reich.
Between lecture tours and her work on her own books, she also wrote “Escape to Life” (1939) and “The Other Germany” (1940) in collaboration with Klaus Mann.

Further reading:
Irmela von der Lühe: I of all people. Die Erzählerin und Journalistin Erika Mann im amerikanischen Exil. In: Thomas Mann und das "Herzasthma des Exils". (Über-)Lebensformen in der Fremde. Die Davoser Literaturtage 2008, hg. v. Thomas Sprecher. (=Thomas-Mann-Studien Bd. 41). Frankfurt/M.: Klostermann 2010, S. 213-230.
Uwe Naumann: „Ruhe gibt es nicht bis zum Schluss“. Klaus Mann 1906–1949. Reinbek 1999, S.226f.
Uwe Naumann: Die Kinder der Manns. Ein Familienalbum. Reinbek 2005, S.152ff.