I write on twentieth-century cultural topics, concentrating on graphic humour, particularly the comic art of The New Yorker, the subject of my The Comic Worlds of Peter Arno, William Steig, Charles Addams and Saul Steinberg (Johns Hopkins University Press, 2005). As well as completing a biography (as yet unpublished) of Saul Steinberg, I've written on other artists such as Jules Feiffer, Quentin Blake, and Alison Bechdel. Most recently I contributed an Afterword to a new edition of Saul Steinberg's first compilation of drawings, All in Line (1945), re-published in 2024 by New York Review Books, with editions in French (Tous en ligne, La Table Ronde, 2025), and Italian (Tuttto in linea, Adelphi, 2026).