Both the Sacred Heart devotion and the Rosary come from the divine hand of friendship personally extended to us against the dehumanization of the computer age. In the words of St. Padre Pio, "The Rosary is THE weapon given us by Mary."
In 1893, Pope Leo XIII issued the encyclical Laetitia sanctae, which proposed a schema for curing the three principal ills of modern society in terms of the Rosary, teaching that:
1. the distaste for simple labor which characterizes the industrial age must yield to the salutary precepts of the Joyful Mysteries;
2. the repugnance for suffering endemic to a pleasure-motivated society must be overcome by living the Sorrowful Mysteries; and
3. the lethal forgetfulness of a future life must be dispelled by ordering all human endeavor to the Glorious Mysteries.
In The Thought of Their Heart, Hertz examines the histories of both devotions, and delves into why these two devotions need to be a part of every Catholic's spiritual life.
Great read and even better examination of conscience, especially dealing with the 7 deadly sins. Definitely a book for nightstand for continued review of your conscience.