Three works of Justin have been preserved.
His First Apology (in the sense of "defense" or "vindication") was addressed (around 155) to the Emperor Antoninus Pius and his adopted sons. (It is perhaps worth noting that some of the fiercest persecutors of the Christians were precisely the emperors who had a strong sense of duty, who were fighting to maintain the traditional Roman values, including respect for the gods, which they felt had made Rome great and were her only hope of survival.) He defends Christianity as the only rational creed, and he includes an account of current Christian ceremonies of Baptism and the Eucharist (probably to counteract distorted accounts from anti-Christian sources).
The Second Apology is addressed to the Roman Senate. It is chiefly concerned to rebut specific charges of immorality and the like that had been made against the Christians. He argues that good Christians make good citizens, and that the notion that Christianity undermines the foundations of a good society is based on slander or misunderstanding.
The Diaolog with Typho the Jew is an account of a dialog between Justin and a Jewish rabbi named Trypho(n) (probably a real conversation with a real rabbi, although it may be suspected that Justin in editing it later gave himself a few good lines that he wished he had thought of at the time), whom he met while promenading at Ephesus shortly after the sack of Jerusalem in 135. Trypho had fled from Israel, and the two men talked about the Jewish people and their place in history, and then about Jesus and whether he was the promised Messiah. A principal question is whether the Christian belief in the deity of Christ can be reconciled with the uncompromising monotheism of the Scriptures. The dialogue is a valuable source of information about early Christian thought concerning Judaism and the relation between Israel and the Church as communities having a covenant relation with God. Toward the end of the dialog, Trypho asks, "Suppose that I were to become a Christian. Would I be required to give up keeping kosher and other parts of the Jewish law?" Justin replies: "Christians are not agreed on this. Some would say that you must give them up. Others, such as myself, would say that it would be quite all right for you, as a Jewish convert to Christianity, to keep kosher and otherwise observe the Law of Moses, provided that you did not try to compel other converts to do likewise, and provided that you clearly understand that keeping kosher will not save you. It is only Christ who saves you." They finally part friends, with Trypho saying, "You have given me food for thought. I must consider this further."
An interesting feature is the dispute about texts. Justin would quote a passage from the Septuagint (LXX), the standard Greek translation of the Jewish Scriptures, and Trypho would reply, "That is not an accurate translation of the Hebrew. You Christians have been tampering with the text!" He never (at least as reportd by Justin) denies that Justin is correctly quoting the Greek manuscripts as they existed at the time, never brings forward an uncorrupted translation that has been preserved by Greek-speaking Jews.
The subsequent history of this dispute about translations is that the Jews, who had produced the LXX translation between 285 and 132 BC, repudiated it as unreliable and produced several subsequent translations, chiefly that of Aquila (around 140), which were close literal translations of the received Hebrew text -- what we may by an anachronism call the Masoretic Text (MT). Many Christians, on the other hand, noted that the LXX is the version usually quoted in the New Testament, even when it differs from the Hebrew. They recalled a Jewish story to the effect that the translation had been produced by 70 (or 72) scholars (hence the name), each working separately, and that their results when compared agreed perfectly; and they took this story as an indication that the LXX was an inspired translation, and that when it disagreed with the Hebrew, so much the worse for the Hebrew! The earliest Latin versions of the Bible (known collectively as the Old Latin (OL)) are translated from the LXX. However, when Jerome was called to produce a new version of the Latin Bible, he translated directly from the Hebrew (except for the Psalms, where he produced two versions), and this reduced the prestige of the LXX in the West. For many years scholars, noting the differences between the LXX and the MT, supposed that the LXX was simply a sloppy translation. However, the Dead Sea Scrolls included many Hebrew manuscripts of portions of Old Testament books (Samuel is the outstanding example) that had readings that agreed with the LXX against the MT. Accordingly, it is now widely held that the LXX is an accurate translation of Hebrew manuscripts representing one of several versions, but not always the version that ultimately prevailed in Hebrew circles and came to be what we call the MT. As for why it happened that the LXX was so often better suited to Christian purposes in proof-texting than the MT, several explanations come to mind:
(a) The early Christians, who were for the most part Greek-speakers, started their search for good proof texts by reading the LXX, and they accordingly found all the places where the LXX gives them what they want and the MT doesn't, while they completely missed all the places where the MT gives them what they want and the LXX doesn't.
(b) The Jews, in their subsequent sorting out of their various manuscript traditions, wherever the rival claims of two readings were otherwise roughly balanced, tended to be more hospitable to a reading that did not furnish aid and comfort to their opponents.
(c) The early Christians, being Greek-speakers steeped in the LXX, tended to remember the details of life of Christ in a way that was colored by the LXX. For example (not a very good example), Matthew (27:34) tells us that before Our Lord was crucified, he was offered wine with gall added. It is unlikely that gall was actually used (it has no relevant pharmacological properties), and I assume that Matthew was using the term simply to refer generically to a bitter-tasting substance. However, his use of this particular term is undoubtedly influenced by Psalm 69:21, considered as a prophecy of the crucifixion. As noted, this is not a very good example, because it does not involve the wording of the LXX. But my point is that a Christian writer, describing an event in the life of Christ while thinking of an Old Testament passage that he believes foreshadows that event, will, without sacrificing factual accuracy, naturally allow that passage to affect his choice of details to mention and words in which to describe them, and if he has been reading the LXX, then the LXX will be a more impressive version to cite than the MT if you are trying to match the event as recorded with the alleged prediction of it.
From the First Apology:
On finishing the prayers we greet each other with a kiss. Then bread and a cup of water mixed with wine are brought to the leader and he, taking them, sends up praise and glory to the Father of the Universe through the name of the Son and of the Holy Spirit, and offers thanksgiving at some length that we have been deemed worthy to receive these things. When the leader has finished the prayers and thanksgivings, the whole congregation assents, saying, "Amen." ("Amen" is Hebrew for "So be it.") Then those whom we call deacons give to each of those present a portion of the consecrated bread and wine and water, and they take it to the absent.
Justin's works are found in the multi-volumed set called The Ante-Nicene Fathers, and in various other collections of early Christian writings. You can find the 38-volume (I think) Ante-Nicene, Nicene, and Post-Nicene Fathers, Edinborough edition, at the web site http://www.newadvent.org/fathers/.
[I'm not sure this is still being sold. However, the same material and much more is available from CCEL.]
Preface of a Saint (3)
Almighty and everlasting God, who found your martyr Justin wandering from teacher to teacher, seeking the true God, and revealed to him the sublime wisdom of your eternal Word: Grant that all who seek you, or a deeper knowledge of you, may find and be found by you; through Jesus Christ our Lord, who lives and reigns with you and the Holy Spirit, one God, for ever and ever.