This was the first book written on the devotion to the Sacred Hearts. As such, it is a basic work in modern spirituality, one of the great devotional treatises which have shaped the history of Catholic prayer life. The characteristic gifts of the devout writer, his elevation of thought and directness of expression, are admirably exemplified in the beloved pages of his Marian masterpiece. The translators are to be warmly thanked for the fidelity and felicity of their English version; it keeps remarkably the spirit and the simplicity of Saint John s original work.