The Heart of St. Gertrude" by Père L. J. M. Cros, S. J., delves into the life and revelations of St. Gertrude the Great, a 13th-century mystic. The book expounds her devotion to the Sacred Heart of Jesus, her insights into divine love, and her powerful intercessory prayers, particularly for the souls in Purgatory. It offers readers a glimpse into her mystical life, highlighting her writings and visions that have inspired countless individuals to seek a closer relationship with God.