Joyce as you may know lived in Trieste a long time and spoke excellent Italian, including dialect. He had already begun to study the language in Dublin as a youth, and was a proficient linguist. Reportedly the Joyces spoke Italian at home, and his two children had Italian names (Giorgio and Lucia). In Trieste, he made friends with writer Italo Svevo (real name, Ettore Schmitz). Svevo (shown in the photo) was a Jew who converted to Catholicism and is taken to be the model of Leopold Bloom, the Irish Jew who is the protagonist of Ulysses. Although to tell you the truth, I've never seen the similarity.
If you read Italian, you can find Svevo's works free on the Liber Liber site, here. The books include his most famous novel, La Coscienza di Zeno, which I recommend.