Saving Europe: First World War Relief and American Identity. Oxford University Press, 2025.
World War I: A Short History. Wiley Blackwell Publishers, 2017.
An English Governess in the Great War: The Secret Diary of Mary Thorp, co-authored with Sophie de Schaepdrijver. Oxford University Press, 2017.
Gender and the Great War, co-edited with Susan R. Grayzel. Oxford University Press, 2017.
Civilians in a World at War, 1914-1918. New York University Press, 2010.
Scouting for Girls: A Century of Girl Guides and Girl Scouts. Bloomsbury (formerly Praeger),
2009.
Scouting Frontiers: Youth and the Scout Movement’s First Century, co-edited with Nelson Block. Cambridge Scholars Press, 2009.
Female Intelligence: Women and Espionage in the First World War. NYU Press, 2003.
On My Honour: Guides and Scouts in Interwar Britain. American Philosophical Society, 2002.
