- Die große Verschwörung (The Great Conspiracy, 1968)
- Die Zeit der Wunder (The Age of Miracles, 1970)
- Das dritte Gesicht (The Third Face, 1972)
- Der Untergang des Abendlandes (The Decline of the West, 1975)
- Die neuen Herren der Welt (The New Masters of the World, 1977)
- Die letzten Tage der Menschheit (The Last Days of Humanity, 1980)
- Das Ende der Welt (The End of the World, 1983)
- Der Tag des Jüngsten Gerichts (The Day of Judgment, 1985)
- Die Apokalypse (The Apocalypse, 1987)
- Das Millennium (The Millennium, 1989)
Freund's work often dealt with themes of conspiracy theories, the occult, and the end of the world. His books have been translated into more than 20 languages.