Tan Books had this to say:
“A short, famous classic on "true devotion to Mary"--an excellent, easy means of attaining holiness and salvation, a way followed by Popes and Saints, but also perfect for lay people. It is at least every bit as good as his True Devotion to Mary! Small but powerful--seems almost divinely inspired!”
The full text is actually available online and it is a disturbing read. I am included a few paragraphs below, not consecutive (pay attention to the paragraph numbers for breaks).
23. The difficulty, then, is how to arrive at the true knowledge of the most holy Virgin and so find grace in abundance through her. God, as the absolute Master, can give directly what he ordinarily dispenses only through Mary, and it would be rash to deny that he sometimes does so. However, St Thomas assures us that, following the order established by his divine Wisdom, God ordinarily imparts his graces to men through Mary. Therefore, if we wish to go to him, seeking union with him, we must use the same means which he used in coming down from heaven to assume our human nature and to impart his graces to us. That means was a complete dependence on Mary his Mother, which is true devotion to her.
28. Chosen soul, this devotion consists in surrendering oneself in the manner of a slave to Mary, and to Jesus through her, and then performing all our actions with Mary, in Mary, through Mary, and for Mary. Let me explain this statement further.
29. We should choose a special feast-day on which to give ourselves. Then, willingly and lovingly and under no constraint, we consecrate and sacrifice to her unreservedly our body and soul. We give to her our material possessions, such as house, family, income, and even the inner possessions of our soul, namely, our merits, graces, virtues and atonements. Notice that in this devotion we sacrifice to Jesus through Mary all that is most dear to us, that is, the right to dispose of ourselves, of the value of our prayers and alms, of our acts of self- denial and atonements. This is a sacrifice which no religious order would require of its members. We leave everything to the free disposal of our Lady, for her to use as she wills for the greater glory of God, of which she alone is perfectly aware.
30. We leave to her the right to dispose of all the satisfactory and prayer value of our good deeds, so that, after having done so and without going so far as making a vow, we cease to be master over any good we do. Our Lady may use our good deeds either to bring relief or deliverance to a soul in purgatory, or perhaps to bring a change of heart to a poor sinner.
31. By this devotion we place our merits in the hands of our Lady, but only that she may preserve, increase and embellish them, since merit for increase of grace and glory cannot be handed over to any other person. But we give to her all our prayers and good works, inasmuch as they have intercessory and atonement value, for her to distribute and apply to whom she pleases. If, after having thus consecrated ourselves to our Lady, we wish to help a soul in purgatory, rescue a sinner, or assist a friend by a prayer, an alms, an act of self-denial or an act of self-sacrifice, we must humbly request it of our Lady, abiding always by her decision, which of course remains unknown to us. We can be fully convinced that the value of our actions, being dispensed by that same hand which God himself uses to distribute his gifts and graces to us, cannot fail to be applied for his greatest glory.
50. Beware, chosen soul, of thinking that it is more perfect to direct your work and intention straight to Jesus or straight to God. Without Mary, your work and your intention will be of little value. But if you go to God through Mary, your work will become Mary's work, and consequently will be most noble and most worthy of God.
55. This devotion faithfully practised produces countless happy effects in the soul. The most important of them is that it establishes, even here on earth, Mary's life in the soul, so that it is no longer the soul that lives, but Mary who lives in it. In a manner of speaking, Mary's soul becomes identified with the soul of her servant. Indeed when by an unspeakable but real grace Mary most holy becomes Queen of a soul, she works untold wonders in it. She is a great wonder-worker especially in the interior of souls. She works there in secret, unsuspected by the soul, as knowledge of it might destroy the beauty of her work.
The premise for such a supreme role of Mary in the lives of Catholics is based on the RCC's teachings of Mary as the mediatrix of all graces, a teaching which is lacking in scriptural support. Without going through each of the paragraphs, I will just say that the elevation of Mary to such a level, despite the reminders of Christ's authority, is idolatrous and blasphemous.
And if you think these ideas are just a fringe of Catholic teaching, be sure to check out historical statements on Mary and the current push by many Catholics to define the fifth Marian dogma. This component of Catholic faith should give Protestants pause.