* The Court of the Vampyre (1972)
* Lilith's Brood:
* Bloodsong (1972)
* Blodets børn (1976)
* The Spawn of Lilith (1978)
* Projekt:Phoenix (1975)
* The Forever Man (1981)
* The Mind Game (1984)
* The Chosen (1985)
* The Gate of the Worlds (1987)
* The Secret of the Rose (1988)
* Shadow Child (1989)
* The Night of the Thirteenth Hour (1991)
* The Timejumpers (1992)
* The Stone Maiden (1994)
* Krystalkraniet (1996)
* The Prophecy of the Ravens (1998)
* The Last Guardian (2000)
* The Doomsday Scroll (2002)
* The Genesis Device (2004)
* The Time Crystal (2006)
Faglitteratur:
* UFO-fænomenet (1974)
* Bermuda-trekanten (1976)
* The Abduction Enigma (1981)
* Gudernes vogne? Sandheden om Erich von Däniken (1986)
* The Roswell Incident (1987)
* Alien Encounters (1989)
* Crop Circles:The Greatest Enigma (1991)
* Area 51:The Truth about Aliens (1993)
* Tegn og vidundere (1994)
* Atlantis Revisited (1996)
* The Nazca Lines:A Message from the Past? (1998)
* The Dead Sea Scrolls:Secrets of the Hidden Gospels (2000)
* The Turin Shroud:The Mysterious Image (2002)
* The Stone Circles:A Cosmic Pilgrimage (2004)
* The Holy Grail:In Search of the Hidden Treasure (2006)