In 1989 Brandt wrote a large book called Sources of Evil: Dualist Themes, where he collected many older works he had read at international or local conferences.
It includes a detailed analysis of Biblical books (Genesis, Ecclesiastes), a careful examination of the Toltec religion, Wycliffe's heresy, and local heretical movements in Dalmatia and Bosnia, especially the phenomenon of the Bosnian Church.
In it, Brandt posits that Serbs controlled the military, the political system, and the economy leading to "Greater Serbian centralisation" in Yugoslavia, with the Croats being exploited and oppressed as a result.
He wrote an autobiography, Living with Contemporaries, where he paints a pessimist image of his life, with not much good to say about his colleagues historians, primarily Jaroslav Šidak and Nada Klaić.
Brandt's claim that his bourgeois origins developed national consciousness and non-communist worldview made him incompatible with the ideological framework of his profession which went against his whole being, is not easy to verify or evaluate.
The available sources indicate that not even the creation of a sovereign Croatian state (which he embraced) managed to pull him away from the lethargy and the feeling of pointlessness as seen from his autobiographic works.