His 2005 monograph on biography and portraiture for the National Portrait Gallery, Insights: The Romantic Poets and their Circle, was unusual in that it included scientists alongside literary writers.

He has also written many drama-documentaries for BBC Radio, most recently The Frankenstein Experiment (2002), and A Cloud in a Paper Bag (2007) about 18th century balloon mania.

October 2008 saw his first major work of biography in over a decade, The Age of Wonder: How the Romantic Generation Discovered the Beauty and Terror of Science, published by HarperPress.

Holmes proposes a radical vision of science before Charles Darwin, exploring the earliest ideas of deep time and deep space, the creative rivalry with the French scientific establishment, and the startling impact of discovery on great writers and poets such as Mary Shelley, Coleridge, Byron and Keats.

[5] In Falling Upwards: How We Took to the Air (2013), Holmes approaches the history of ballooning by presenting biographies of French, English, and American balloonists.