Lotte eta Luisa, hau bizki parea!

Blurb

Lottie and Lisa is a 1949 novel by Erich Kästner, about twin girls separated at birth who meet at summer camp.
The book originally started out during World War II as an aborted movie scenario. In 1942, when for a brief time Kästner was allowed by the Nazi authorities to work as a screenwriter, he proposed it to Josef von Báky, under the name “The Great Secret”, but before he could proceed the Nazis once again forbade him to work.
After the war, Kästner worked the idea into a highly successful book. Subsequently, it has been adapted into film many times, as well as being translated into various languages.