His ongoing projects include numerous studies and a co-written book on world art history, and a history of the Habsburgs. He is co-editor and a major contributor to a multi-volume history of art and architecture in the Iberian world through the ages. His recent books include Rudolf II: The Life and Legend of the Mad Emperor, London, Reaktion Books, and Chicago, University of Chicago Press, 2025, and an edition and introduction to a new translation of Julius von Schlosser, The Cabinets of Art and Wonder of the Late Renaissance, Los Angeles, Getty Research Center, 2021.  Giuseppe Arcimboldo. Complete 500^th Anniversary Edition, Cologne, Taschen, will be published in 2026.