Few ancient Christian authors attempted anything like a complete commentary on the Gospel of John, among them Origen, John Chrysostom and Augustine. Of these, Augustine's must count as the greatest. Unlike Origen's, it has come down to us in its entirety, and of the others that remain it is certainly the most theologically profound. John's gospel allows Augustine to range broadly over themes that were his life's work -the Trinity, the person of Christ, the nature of the Church and its sacraments, the fulfillment of the divine plan.
The 124 homilies that constitute Augustine's commentary, however, are masterpieces not only of theological profundity but also of pastoral engagement. In the question-and-answer style that he frequently employs, for example, one can sense Augustine's real awareness of his congregation's struggles with the gospel text. And the congregation's response to Augustine, which he frequently alludes to, is an indication of the success of his dialogical preaching style.
The Johannine literature drew out the best in Augustine. The Homilies on the Gospel of John are the indispensable complement to The Homilies on The First Epistle of John, published in this series, and they should be a part of any serious theological library.

Saint Augustine of Hippo (13 November 354 - 28 August 430 AD) was a Roman African, Manichaean, early Christian theologian, doctor of the Church, and Neoplatonic philosopher from Numidia. His writings influenced the development of the Western Church and Western philosophy, and indirectly all of Western Christianity. He was the bishop of Hippo Regius in North Africa and is viewed as one of the most important Church Fathers of the Latin Church for his writings in the Patristic Period.
Augustine was one of the most prolific Latin authors in terms of surviving works. He authored more than one hundred separate titles, including apologetic works against the heresies of the Arians, Donatists, Manichaeans, and Pelagians; texts on Christian doctrine; critical examinations of the bible; and many sermons and letters. Augustine is best known for his Confessions, a personal account of his earlier life, and De civitate Dei (The City of God), which he wrote to restore the confidence of his fellow Christians after the sack of Rome.