Written by the spiritual director of St. Margaret Mary (1647-1690), the book comes from the pen of a man intimately familiar with every aspect of the revelations given by Our Lord to this famous Saint. Thus, the book is actually the "key" to understanding the importance and the centrality of the Sacred Heart devotion for our lives as Catholics.

The Devotion to the Sacred Heart of Jesus was actually commissioned by Our Lord Himself through St. Margaret Mary, and as the author neared completion of it, the Saint told him that Our Lord said it was so completely in accord with His wishes that it would never be necessary to make any change in it. Later she revealed to Fr. Croiset that it was Our Lord Himself who had inspired him with the ideas in this book and that it was so pleasing to Him that "none other but Himself could have arranged everything so much to His wishes."

This present translation is the first in English of the unabridged book and contains Fr. Croiset's full sketch of the Saint's life, as well as all her prayers in honor of the Sacred Heart, and a complete list of the Promises of the Sacred Heart.