In his latest work of nonfiction, British author Tim Parks (“Europa,” “Italian Ways”) couches historical inquiry in the form of a nearly 400-mile hike up the spine of Italy. He took this arduous walk with his romantic companion, translator Eleonora Gallitelli, in the pre-COVID-19 summer of 2019.

Their route was determined by the snaking monthlong retreat Giuseppe Garibaldi made with 4,000 volunteer fighters and his pregnant young wife in 1849, following the collapse of the brief-lived Roman Republic.