Schreiber conducted extensive research into the German-Italian relations prior and during World War II, including the fate of the Italian soldiers interned by Germany after the occupation of the country by Germany in 1943. His 1990 book Deutsche Kriegsverbrechen in Italien 1943/45. Geschraten, Verachtet, vergessen" [The Italian Military Internees in the German Sphere, 1943 to 1945: Betrayed, Despised, Forgotten] is considered a standard work on the topic.[2] Schreiber was one of the first German historians to write about the Waffen-SS and Wehrmacht crimes in Italy, including the Sant'Anna di Stazzema massacre, in his work Deutsche Kriegsverbrechen in Italien. Täter, Opfer, Strafverfolgung [German War Crimes in Italy—Culprits, Victims, Prosecution].[3]
Schreiber contributed to volumes III The Mediterranean, South-East Europe, and North Africa 1939–1942 and VIII The Eastern Front 1943-1944: The War in the East and on the Neighbouring Fronts of Germany and the Second World War. In Volume III, Schreiber focused on "Hitler's failure to establish true alliances rather than satellite relationships in which Germany always maintained the upper hand".[4] Historian Mark Mazower called Volume III "definitive" and praised it for its "range and intellectual energy". He notes that the authors are widely read on the topics and are familiar with the existing controversies in the field, expertly guiding the reader through them.[5]
Die italienischen Militärinternierten im deutschen Machtbereich 1943 bis 1945. Verraten – Verachtet – Vergessen (= Beiträge zur Militärgeschichte. Band 28). Oldenbourg, München 1990, ISBN3-486-55391-7.
Deutsche Kriegsverbrechen in Italien. Täter, Opfer, Strafverfolgung. Beck, München 1996, ISBN3-406-39268-7.
Der Zweite Weltkrieg. Beck, München 2002, ISBN3-406-44764-3. (5. Auflage 2013)
Kurze Geschichte des Zweiten Weltkriegs. Beck, München 2005, ISBN3-406-52953-4.