Armstrong's most recent book is How Literature Plays with the Brain: The Neuroscience of Reading and Art, (Johns Hopkins University Press, hardcover and e-book 2013; paperback 2014). He has also published four other books of literary criticism and theory: The Phenomenology of Henry James (U of North Carolina P, 1983), The Challenge of Bewilderment: Understanding and Representation in James, Conrad, and Ford (Cornell UP, 1987), Conflicting Readings: Variety and Validity in Interpretation (U of North Carolina P, 1990; Spanish and Arabic translations), and Play and the Politics of Reading: The Social Uses of Modernist Form (Cornell UP, 2005). He has also edited Norton Critical Editions of E. M. Forster, Howards End (W. W. Norton, 1998) and of Joseph Conrad, Heart of Darkness (4th ed., W. W. Norton, 2006).
Before coming to Brown as Dean of the College in 2001, Armstrong was Dean of Arts and Sciences at SUNY-Stony Brook and Humanities Dean at the University of Oregon. He has also taught at the University of Virginia and Georgia Tech and has been a visiting professor at the University of Copenhagen and the Free University of Berlin.
Armstrong has held fellowships from the Humboldt Foundation and the National Endowment for the Humanities. He also received a grant from the Teagle Foundation to chair an inter-institutional working group that wrote a white paper on "The Open Curriculum: An Alternative Tradition in Liberal Education." The opening chapter of his book Conflicting Readings was awarded the William Riley Parker Prize for an Outstanding Article in PMLA . His chapter on Nostromo in The Challenge of Bewilderment won the Twentieth Century Literature Prize in Literary Criticism.
His fifth Norton Critical Edition of Heart of Darkness, with a newly edited text and a substantially revised apparatus, is forthcoming (2016). Armstrong has also prepared a scholarly edition of Henry James's posthumously published, unfinished novel The Ivory Tower for the Cambridge University Press series of his collected fiction (forthcoming 2016-17).
He is currently working on a book on neuroscience and narrative.