Professor O'Sullivan specializes in 18th-century English literature, minority literature, popular culture, and Florida studies.
In addition to articles on literature and pedagogy, he has published The Florida Reader (1991); Florida in Poetry (1995); Smith's Book of Job (1996); Crime Fiction and Films in the Sunshine State (1997); Shakespeare's Other Lives (1997); Elizabeth and Orange Pulp (2000); Shakespeare Plays the Classroom (2003).