Tannus wrote manuscripts about his Maronite sect, Arab and Islamic history, the colloquial Arabic of Mount Lebanon and his family, some of which were lost. The most important of his works was Akhbar al-a'yan fi Jabal Lubnan, which was supervised by Butrus al-Bustani, and published in separate parts in 1855 and 1859. In it he described the natural and political geography of Mount Lebanon, documented the genealogies of its feudal families, and chronicled the history of its rule by families, such as the Buhturids, the Ma'ns, the Assafs, the Sayfas and the Shihabs. His chronicle has been one the main sources for modern-day histories of Mamluk and Ottoman Lebanon.