In On the Sanctification of According to the Needs of Our Times, the famous Thomistic theologian Fr. Garrigou-Lagrange, O.P. expounds in a disciplined manner upon the specific holiness of the priesthood and the supernatural fruitfulness of the priestly apostolate. Steeped in Sacred Scripture, St. Thomas Aquinas and other traditional Catholic sources, the author presents the traditional Catholic teaching on the priestly vocation and the means necessary for attaining the holiness required by this lofty state of life.
Réginald Marie Garrigou-Lagrange, O.P. (February 21, 1877, Auch, France – February 15, 1964, Rome) was a Catholic theologian and, among Thomists of the scholastic tradition, is generally thought to be the greatest Catholic Thomist of the 20th century. He taught at the Pontifical University of St. Thomas Aquinas, commonly known as the Angelicum, in Rome from 1909 to 1960.
Father Garrigou-Lagrange initially attracted attention when he wrote against the theological movement later called Modernism. He is also said to be the drafter or "ghostwriter" of Pope Pius XII's 1950 encyclical Humani Generis, subtitled "Concerning Some False Opinions Threatening to Undermine the Foundations of Catholic Doctrine."
He is best known for his spiritual theology. His magnum opus in the field is The Three Ages of the Interior Life, in which he propounded the thesis that infused contemplation and the resulting mystical life are in the normal way of holiness of Christian perfection.
This book is also really helpful for those discerning a call to the priesthood, it lays out what should always have been the program for those seeking to be a part of the Priesthood of Jesus Christ. However, even if you are not intent on becoming a priest, we must remember that the whole Mystical Body of Christ is a Priestly Nation, therefore this book is still good to read in order to enter more intently on the Priesthood of All Believers. Fr. Lagrange does a spectacular work covering Prayer and Intellectual Formation to the Moral and Theological Virtues as it relates to the Gifts and The Beatitudes; with special treatment on the Eucharistic Christ to finish the book. This book is small and can probably be completed in about a week, but it will be referred to again and again for its insights, this in union with "The Priest Union With Christ" by Fr. Lagrange makes for an insightful read.