Upon retirement, Bieri pursued his interest in English Romantic poetry and in 2005 published a two-volume biography of Percy Bysshe Shelley (University of Delaware Press, 2004 & 2005).
Following his departure from active life, Bieri explored his enthusiasm for English Romantic poetry and subsequently authored a comprehensive two-volume biography of Percy Bysshe Shelley, published by the University of Delaware Press in 2004 and 2005.