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 career, Bieri focused on his interest in English Romantic poetry and published a detailed biography of Percy Bysshe Shelley, which appeared in two volumes from the University of Delaware Press in 2004 and 2005.