* The Last Witnesses
* The Devil's Cradle
* The Vatican Agenda
* The Dante Club
* The Vatican Conspiracy
* The Book of Revelation
* The Dead Sea Scrolls
* The Ark of the Covenant
* The Spear of Destiny
* The Shroud of Turin
Non-fiction
* The Vatican in the Age of Enlightenment
* Cardinals of the Holy Roman Church: Biographical Dictionary, Volume 2
* The Catholic Encyclopedia, Volume 1
Short stories
* "The Hand of God"
* "The Devil's Advocate"
* "The Last Confession"
* "The Judas Kiss"
* "The Final Judgment"
Other works
* The Vatican: Power, Politics, and Prophecy (editor)
* The Dead Sea Scrolls: Uncovering the Secrets of Qumran (editor)
* The World of the Gospels (editor)
* The Oxford Encyclopedia of the Bible (contributor)