Following the advice of C.S. Lewis, it is needful to read the original sources of writing and often it is easier than “some dreary modern book ten times as long, all about ‘isms’ and influences and only once in twelve pages” saying what the original writer actually said.
There are many cheap Kindle books with writings of the church fathers which can be read not just on a Kindle but on your computer or on your phone or tablet with a free Android app or iPhone app. Most of these are only 99 cents and at most just a dollar or two more.
Church Father Collection The Complete Ante-Nicene & Nicene and Post-Nicene Church Fathers Collection: 3 Series, 37 Volumes, 65 Authors, 1,000 Books, 18,000 Chapters, 16 Million Words — All of this for less than the price of the average Starbucks drinks!
Apostles The Apostolic Constitutions — By tradition this is the work of the Twelve Apostles, whose instructions, whether given by them as individuals or as a body, are supposed to be gathered and handed down by the compiler, Clement of Rome The Didache — Teaching of the Lord to the Gentiles (or Nations) by the Twelve Apostles and is mentioned in Eusibius Church History.
St. Athanasius On The Incarnation (With Active Table of Contents) — Explains the profound significance of the Incarnation and the Crucifixion. The Life of St. Anthony the Great — St. Athanasius was a friend of St. Anthony and wrote the biography of this desert father.
St. Basil the Great Collected Letters Nine Homilies of Hexaemeron — Addresses the Creation of the World in Genesis. On the Holy Spirit
St. Benedict The Rule of St. Benedict — Born around 470 AD, while this saint is known as the Father of Western Monastism and as a prominent role in the Latin Church, he is thoroughly a saint in the Orthodox Church.
St. Clement of Rome The Writings of Clement of Rome
St. Cyril of Alexandria On the Unity of Christ
St. Cyril of Jerusalem The Catechetical Lectures of St. Cyril of Jerusalem
St. Dionysius the Areopagite The Works of Dionysius the Areopagite
St. Ephraim the Syrian Hymns and Homilies of St. Ephraim the Syrian
Eusebius of Caesarea History of the Church
St. Gregory of Nazianzus aka St. Gregory the Theologian The Orations
St. Gregory of Nyssa Collection of Writings On the Holy Trinity and select works
St. Irenaeus Against Heresies
St. Isaac the Syrian Mystic Treatises by Isaac of Niveveh
St. John Chrysostom The Complete Works of Saint John Chrysostom (33 Books With Active Table of Contents) — This is a very comprehensive collection of the writings of the Golden Mouth which are foundational to Orthodox theology.Note: There are many 99 cent writings available such as On the Priesthood, Homilies on the Gospel of St. Matthew and St. John, and other epistles, but these all seem to be included in this one collection.
St. John of Damascus St. John Damascene on Holy Images — The famous treatise on the veneration of icons, which was confirmed as part of our Faith at the 7th Ecumenical Council
An Exact Exposition of the Orthodox Faith
St. Leo the Great Letters and Sermons of Pope St. Leo I (The Great)
St. Seraphim of Sarov On Acquisition of the Holy Spirit