Christian's research focuses on the social and cultural history of modern Europe, especially, but not exclusively Germany and Italy. His first book (published by Oxford University Press in 2009; German translation published by Suhrkamp Verlag in 2011) is about the suicides of ordinary people, Jews and Nazis in Germany between 1918 until 1945, from the end of the first world war until the end of the second world war. He is interested in conceptualising a new social and cultural history of modern Germany, one firmly grounded within social theories, while bringing back the individual into history. This new social and cultural history is firmly contextualised with politics.
Christian has also worked on state terror, especially on repression in Nazi Germany. With Nikolaus Wachsmann, he has been working on a major AHRC research project at Birkbeck on concentration camps in Nazi Germany before the Holocaust. Its two chief outcomes are a special issue of the Journal of Contemporary History and a monograph (to be published by the University of Nebraska Press in 2012).
Christian is currently working on two related projects. One is a history of organised crime in twentieth-century Germany and Italy (funded by a two-year Leverhulme Early Career Fellowship), the other is a history of what he calls the 'entanglement' between Fascist Italy and Nazi Germany.