According to María de Ágreda, the book was to a considerable extent dictated to her by the Blessed Virgin Mary and regarded the life of the Virgin Mary and the divine plan for creation and the salvation of souls. The work alternates between descriptions of the Trinity, the Virgin Mary's life, and the spiritual guidance she provides to the author, by whom her words were reproduced for the spiritual benefit and growth of the reader. The book describes at length the various virtues, and how the reader should live in order to see them reflected in their own life, with the Virgin Mary as their model for sanctity. The work has the Imprimatur of several Popes and Bishops and appeals primarily to those who believe in "private revelation" and the sanctity of Mary.

Volume one deals with the Conception of the Blessed Virgin Mary. "The Sacramental Mysteries wrought by the Most High in the Queen of Heaven from the time of her Immaculate Conception until the Incarnation of the Word in her virginal womb, and how much merit she herself acquired through Divine Grace by profiting from the favors conferred upon her during those first fifteen years of her life." - Summary by Wikipedia and Introduction