Charles Austin Beard: The Return of the Master Historian of American Imperialism. Ithaca: Cornell University Press, 2018.
The Education of an Anti-Imperialist: Robert La Follette and U.S. Expansion. Madison: University of Wisconsin Press, 2013.
Apostles and Agitators: Italy’s Marxist Revolutionary Tradition. Cambridge: Harvard University Press, 2003.
The Aldo Moro Murder Case. Cambridge: Harvard University Press, 1995.
The Revolutionary Mystique and Terrorism in Contemporary Italy. Bloomington: Indiana University Press, 1989. (Revised Second Edition published in 2021)
Byzantium for Rome: The Politics of Nostalgia in Umbertian Italy, 1878-1900. Chapel Hill: University of North Carolina Press, 1980.