- The Red Wall (2013)
- The Black Pope (2014)
- The Vatican Trilogy (2015)
- The Secret of the Vatican (2016)
- The Last Secret (2017)
- The Brotherhood (2019)
- The Vatican Agenda (2020)
- The Vatican Conspiracy (2021)
- The Vatican Tapes (2022)
Occa's books have been translated into several languages and have sold more than 2 million copies worldwide. He is a regular contributor to several Italian newspapers and magazines, and he has appeared on several television and radio programs.