This book was composed by St. Alphonsus Ligouri during a time of criticism of Marian devotions. St. Ligouri brings his considerable knowledge of Scripture and the Church Fathers to bear on the issue, showing their devoted support of Mary. St. Ligouri also includes the Marian prayers and practices that he is familiar with.

The book is divided into five sections:

1. The Salve Regina (Hail Holy Queen), where he explains how God graced the world with Mary as a "Gate of Heaven", echoing St. Bonaventure's words, "No one can enter Heaven unless by Mary, as though through a door."

2. The feasts, such as the Immaculate Conception, Nativity, dedicated to St. Mary.

3. The Seven Sorrows of Mary's "martyrdom".

4. The ten virtues of the Virgin Mary.

5. Prayers, meditations and devotions to Mary.

Lastly there is an appendix defending Mary's role as a mediatrix.