St. Catherine of Siena (1347 - 1380) was almost single-handedly responsible for bringing the Papacy back to Rome after the long Avignon Papacy. Her book, The Dialogue, demonstrates advanced theological understanding, and includes direction in how to progress in the spiritual life, and also the words of God spoken directly to her. 

Links

The Dialogue, with Introduction: https://www.paulistpress.com/Products/2233-2/catherine-of-siena.aspx

For comparison, the Diary of St. Faustina: https://shopmercy.org/diary-of-saint-maria-faustina-kowalska.html

The letters of St. Catherine online: http://www.domcentral.org/trad/cathletters.htm

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Dr. Papandrea's Homepage:  https://jimpapandrea.wordpress.com/

Dr. Papandrea's latest book is The Original Church: What it Meant - and Still Means - to Be a Christian: https://scepterpublishers.org/products/the-original-church-what-it-meant-and-still-means-to-be-a-christian

Dr. Papandrea's YouTube channel, The Original Church: https://www.youtube.com/@TheOriginalChurch

Theme Music: Gaudeamus (Introit for the Feast of All Saints), sung by Jeff Ostrowski. Courtesy of Corpus Christi Watershed:  https://www.ccwatershed.org/