They are freely available for anyone to read. They are the writings of the early Fathers of the Church, starting with the letter of Clement to the Corinthains in about 90 AD.
Here's a comprehensive site that has them all:
http://www.newadvent.org/fathers/
Some interesting quotes:
ST. IGNATIUS OF ANTIOCH
St. Ignatius became the third bishop of Antioch, succeeding St. Evodius, who was the immediate successor of St. Peter. He heard St. John preach when he was a boy and knew St. Polycarp, Bishop of Smyrna. Seven of his letters written to various Christian communities have been preserved. Eventually, he received the martyr's crown as he was thrown to wild beasts in the arena.
"Consider how contrary to the mind of God are the heterodox in regard to the grace of God which has come to us. They have no regard for charity, none for the widow, the orphan, the oppressed, none for the man in prison, the hungry or the thirsty. They abstain from the Eucharist and from prayer, because they do not admit that the Eucharist is the flesh of our Savior Jesus Christ, the flesh which suffered for our sins and which the Father, in His graciousness, raised from the dead."
"Letter to the Smyrnaeans", paragraph 6. circa 107 A.D.
ST. JUSTIN MARTYR
St. Justin Martyr was born a pagan but converted to Christianity after studying philosophy. He was a prolific writer and many Church scholars consider him the greatest apologist or defender of the faith from the 2nd century. He was beheaded with six of his companions some time between 163 and 167 A.D.
"This food we call the Eucharist, of which no one is allowed to partake except one who believes that the things we teach are true, and has received the washing for forgiveness of sins and for rebirth, and who lives as Christ handed down to us. For we do not receive these things as common bread or common drink; but as Jesus Christ our Savior being incarnate by God's Word took flesh and blood for our salvation, so also we have been taught that the food consecrated by the Word of prayer which comes from him, from which our flesh and blood are nourished by transformation, is the flesh and blood of that incarnate Jesus."
"First Apology", Ch. 66, inter A.D. 148-155.
Pope Clement I
"Through countryside and city [the apostles] preached, and they appointed their earliest converts, testing them by the Spirit, to be the bishops and deacons of future believers. Nor was this a novelty, for bishops and deacons had been written about a long time earlier. . . . Our apostles knew through our Lord Jesus Christ that there would be strife for the office of bishop. For this reason, therefore, having received perfect foreknowledge, they appointed those who have already been mentioned and afterwards added the further provision that, if they should die, other approved men should succeed to their ministry" (
Letter to the Corinthians 42:4–5, 44:1–3 [A.D. 90]).