* _Zero Sum_ (2003)
* _Black Water: A Novel_ (2006)
* _The Last Centurion_ (2008)
* _The Emperor's Falcons_ (2009)
* _The Legion's Wrath_ (2011)
* _The Sword of Macedon_ (2012)
* _The Death of Kings_ (2013)
* _The Gates of Rome_ (2014)
* _Imperator: Rise of the Tyrant_ (2015)
* _Imperator: Fall of the Tyrant_ (2016)
* _Caesar: Rise to Power_ (2017)
* _Caesar: Master of the World_ (2018)
* _Caesar: Destroyer of Worlds_ (2019)
* _Augustus: Rise to Power_ (2020)
* _Augustus: Master of the World_ (2021)
* _Augustus: Destroyer of Worlds_ (2022)
* Non-Fiction:
* _The Story of the CIA: From the Shadows to the Light_ (2010)