Egan is the author of more than 80 professional articles and ten books, including:

• Henrik Ibsen: The Critical Heritage (Routledge and Kegan Paul, 1972, Taylor & Francis, 2000)
• Extreme Situations: Literature and Crisis from the Great War to the Atom Bomb (Macmillan, 1979) [with David Craig]
• Huckleberry Finn: Race, Class and Society (Sussex University Press, 1977)
• Henry James: The Ibsen Years (Vision Press, 1972)

Egan's most recent book is the variorum edition of The First Part of the Tragedy of King Richard the Second: A Newly Authenticated Play by William Shakespeare, with an introduction, notes and critical commentary (Edwin Mellen Press, 2006), which won the 2006 Adele Mellen Prize for Distinguished Contribution to Scholarship.