What God is by Nature, Mary is by Grace is a compendium of the teachings on the Blessed Virgin Mary found in the pages of Luisa Piccarreta's Book of Heaven. The Book of Heaven is a 36 volume collection of her writings on the Divine Will, as revealed by the Lord and by His Mother. The current book is a detailed narrative report and description of over 250 dated entries about Mary contained in Luisa's opus. This is my fourth book on the writings of Luisa Piccarreta. The first three presented overviews of the first 21 volumes of her revelations. This book is more than an overview, and concentrates solely on teachings about the Blessed Virgin Mary's life on earth and in heaven as lived in the Divine Will. Luisa's writings reveal the hitherto unknown extent of the true greatness, height and sublimity of the life of the Mother of God. This is a good faith sharing of my work on this very difficult and abstruse topic, based on the best available English translations of her work, and is not intended to be considered authorized, official, or definitive. Any eventual publication of a Church-approved English translation of her works should not affect the meaning or sense of the present book. The source references to the entries from Luisa's 36 volume Book of Heaven are given after each use, and indicate the volume number and the date of the entry. The Servant of God Luisa Piccarreta was a twentieth century mystic from southern Italy (1865-1947). She spent over 60 years of her life confined to bed, essentially subsisting only on the Holy Eucharist. She was a victim soul, who experienced intense sufferings, as well as visits and revelations from Jesus and Mary. For a time her spiritual advisor was St. Annibale di Francia, instrumental in obtaining Church approval for the first 19 volumes of Luisa's work, until his death. Her writings center on the importance of the Divine Will in the life of Christians, and the coming of the Kingdom of the Divine Will, as foretold in the Lord's prayer: "Thy Kingdom come, Thy will be done, on earth at it is in heaven." Her Cause for Beatification and subsequent Canonization is being considered by the Vatican's Congregation for the Causes of Saints.