• Islamic History
• Historiography
• Advanced Arabic Text Research
• Comparative Mediaeval Studies
• Myth and Religion in Literature
• Sufism
• History of Ireland

Publications:

Gilgamesh, new edition with new afterward, Houghton Mifflin & Co., 2003

Al-Hallaj, Curzon Press Ltd., London, 1995.

Hallaj, Mystic and Martyr, Abridgment, Princeton University Press, 1994.

Testimonies and Reflections, Notre Dame University Press, 1989.

Memoir of a Friend: Louis Massignon, Bibliography, Notre Dame University Press, 1988.

The Passion of al-Hallaj by Louis Massignon, 4 vols., Bolligen Series XCVIII, Princeton University Press, 1983. (Editor and translator).

The Death of al-Hallaj, a Dramatic Narrative, Notre Dame University Press, 1979.

Gilgamesh, A Verse Narrative, Houghton Mifflin & Co., Boston, 1970; Mentor Edition, NAL, New York, 1972; 1977; 1984; 1992; 2002; currently its 31st printing. (National Book Award Nominee, 1971).

Two Statesmen of Mediaeval Islam, a study, Mouton & Co., The Hague, 1972.
"Hasan Basri, Monograph," Sufi, Issue 41, 1999.

"The Ancient Near East," essay for the Dearborn Press Encyclopedia of Historians and Historical Writing, London, 1996.

"Moments in Passage," memoir, The Phoenix, Morningstar Press, Haydenville, Mass. Vol. 7, 3-4, Spring 1980; Vol. 8 1-2, Fall 1980.

Translations in Verse of the Arabic Diwan of al-Hallaj, Introduction to Classic Arabic Literature, ed. I. Lichtenstadter, Twayne, New York, 1974.

"Arab Algerian Literature Revisited," study, Humaniora Islamica, I/1973.