This book was composed during the lifetime of St. Margaret Mary Alacoque and published in 1691, the year after her death.

The following is taken from the back cover of TAN's 1988 publication of the book:

    "Devotion to the Sacred Heart of Jesus by Fr. John Croiset, S.J. is not 'just another book on the Sacred Heart devotion,' but it can be truly said to be the book on this devotion.  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 true Catholics.
    But more even than being the book on the Sacred Heart devotion, Fr. Croiset's work is a revelation to us all just why so few people become great saints, just why so few Catholics -- despite going frequently to the Sacraments -- fail really to grow in the life of grace and make great progress in the spiritual order.
    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.'"

I should add that the sub-heading of this classic book is "How to Practice the Sacred Heart Devotion."

I should further add that the following is the interesting/fascinating and truly amazing continuation of the description of the book found on the back cover as seen in the above quote:

     "Appearing in print during the first year after the Saint's death, the book was an instant success and was translated into all the European languages except English.  For 13 years it was the primary vehicle for making universally known the devotion to the Sacred Heart of Jesus.  But then, through a technicality, it was placed on the 'Index of Forbidden Books,' to go into obscurity until modern times, when the Bishop of Sarajevo (Yugoslavia) discovered this treasure and asked the Sacred Congregation of the Index to reexamine it.  They did, and approved it without change, thus fulfilling St. Margaret Mary's prophecy that it would become forgotten for a time but then would come to light again.
     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, which number many more than the famous '12 Promises.'
     In all, Devotion to the Sacred Heart of Jesus by Fr. John Croiset, S.J., rather than a boring book on a dry subject, is the best explanation of the central devotion of the Catholic Church and in the process is a challenge to every Catholic to raise himself to that level of the spiritual life Our Lord expects and requires of him and which alone will enable him to become a great saint."