Sr. Thomas Mary, O.P. writes:
Beginning a commentary on THE SECRET OF MARY
by St. Louis Marie de Montfort
(Abbreviations in references: SM=The Secret of Mary; TD=True Devotion to the Blessed Virgin.)
THE SECRET of MARY was composed by St. Louis Marie as a concise exposition of his lengthier work TRUE DEVOTION to the BLESSED VIRGIN. It has been widely distributed in pamphlet form.  In these opening years of the 21st century, St. Louis de Montfort’s Marian devotion is spreading throughout the world as he himself foretold (SM #59; TD #47- 49).
St. Louis emphasizes that this particular devotion to Mary is a secret because he wants us to realize its supernatural excellence. He explains that it was taught him to him by the Most High and has an efficacious and transforming power in the lives of those who truly enter in and use it for their personal holiness, for this secret works its effects in a soul only in proportion to the use made of it (SM #1,2). One must go beyond its exterior practices, necessary though they be, and attain to its essential interior practice in order to find, through grace, the supernatural treasure hidden within. Just as our Lord and Savior Jesus Christ became the child of Mary, so too, the adopted child of the Father embraces Mary as his Mother and gives himself completely to her maternal care. True Devotion to Mary is a way of life and is meant to enclose the soul in the secret abyss of her wisdom. As a special gift of God it demands a high degree of theological faith, hope and charity.
St. Louis cautions us to beware, then, of remaining inactive while possessing this gift of grace, as did the wicked servant in the parable of the pounds. He kept his pound laid up in a napkin through fear and was condemned (Lk 19: 20-24). Rather those who receive this gift should persevere in using it in order to understand its value. He counsels the fortunate person to thank God all the days of your life, for the grace He has given you to know a secret you do not deserve to know (SM #3).
St. Louis guards his secret with a holy jealousy that denotes respect for divine things, just as the Lord himself warns, do not give what is holy to dogs, or throw your pearls before swine, lest they trample them underfoot, and turn and tear you to pieces (Mt 7:6). It is meant for those who, recognizing their innate poverty and nothingness without the divine mercy, are yet ardently seeking to know, love and serve God, as it is written: You shall love the Lord, your God, with all your heart, and with all your soul, and with all your strength (Deut 6:5). Indeed the very first word of The Secret of Mary indicates that it is addressed to the predestined soul  (#1)!
And those he predestined he also called;
and those he called he also justified;
and those he justified he also glorified (Rom 8:20).
1. The Collected Writings of St. Louis Marie de Montfort have been newly translated and published in one volume: God Alone (Bayshore, N.Y.: Montfort Publications, 1988). The Secret of Mary (with earlier translation) continues to be available in pamphlet editions. True Devotion to the Blessed Virgin, translated by Fr. F. W. Faber (Montfort Publications, 1950), is now available from Tan Books, Rockford Il.
2. Prédestinée is the word St Louis uses in the original French text. It is used by Fr. Faber in his translation of True Devotion and in the pamphlet editions of The Secret of Mary. In the volume God Alone it has been translated as chosen. Predestination is a Biblical word rich in content and it will continue to be used in these on-going commentaries. Because this word has been open to misunderstanding in the past, a subsequent commentary will give its theological meaning according to St. Thomas Aquinas and its spiritual reverberations in the writings of Blessed Elizabeth of the Trinity. See Hans Urs von Balthasar, Two Sisters in the Spirit (San Francisco: Ignatius Press, 1992).