* The Roads of Exile (1977)
* The Circle of Time (1981)
* Timebound (1982)
* Children of the Sky (1983)
* Legacy (1984)
* Beyond This Horizon (1985)
* The Genesis Machine (1987)
* Voyage of the Star Wolf (1989)
* Mindbridge (1990)
* Crash Dive (1992)
* The Tunguska Event (1993)
* The Mars Conspiracy (1995)
* The Genesis Device (1996)
* The Last Battle (1997)
* The Omega Event (1999)
* The Doomsday Virus (2000)
* Apocalypse Dawn (2002)
* Extinction Horizon (2003)
* Genesis Rising (2005)
* Armageddon's Arrow (2007)
* Last Stand at Terra (2009)
* Earthfall (2011)
* Revelation's Fire (2013)
* Redemption's Dawn (2015)
Short Stories:
* "The First Voyage" (1979)
* "In the Shadow of the Sphinx" (1980)
* "The Last Days of Pompeii" (1982)
* "The Tower of Babel" (1983)
* "The City of Atlantis" (1984)
* "The Hanging Gardens of Babylon" (1986)
* "The Fall of Troy" (1987)
* "The Battle of Thermopylae" (1989)
* "The Trojan War" (1990)
* "The Odyssey" (1992)
* "The Iliad" (1993)
* "The Fall of Rome" (1994)
* "The Age of Charlemagne" (1996)
* "The Crusades" (1998)
* "The Hundred Years' War" (2000)
* "The War of the Roses" (2001)
* "The Italian Renaissance" (2003)
* "The Age of Discovery" (2005)
* "The Thirty Years' War" (2007)
* "The French Revolution" (2009)
* "The Napoleonic Wars" (2011)
* "The American Civil War" (2013)
* "World War I" (2015)
* "World War II" (2017)
Nonfiction:
* The Time Traveler's Guide to the Future (2007)
* The Science of Time Travel (2009)
* The Physics of Space-Time (2011)
* The Future of Humanity (2013)
* The Search for Extraterrestrial Life (2015)
* The Mysteries of the Universe (2017)