Magnum Crimen
Novak wrote that he spent more than 40 years collecting documents and books to write his book. He started collecting this material during his secondary school days, continued it as a university student, and as a member of the Austrian Institute of History in Vienna, Austria, then as a university professor in Zagreb and Belgrade. He worked on three books, of which Magnum crimen is the last, the first two parts of are the Magnum tempus and the Magnum sacerdos. In 1941, after the destruction and occupation of the Kingdom of Yugoslavia, Novak was forced to destroy all material he had collected. He was in danger of being arrested and killed by the German occupying forces and their collaborators in Belgrade. He was among the first ten people arrested in Belgrade by Germans, but managed to survive and continue work on this book after liberation of Belgrade in October 1944.