I found this on Wikipedia (I’ve added bold text myself to highlight points):
Doctrine of the logos
Justin’s use of the idea of the logos has always attracted attention. It is probably too much to assume a direct connection with Philo in this particular. The idea of the Logos was widely familiar to educated men, and the designation of the Son of God as the Logos was not new to Christian theology. The significance is clear, however, of the manner in which Justin identifies the historical Christ with the rational force operative in the universe, which leads up to the claim of all truth and virtue for the Christians and to the demonstration of the adoration of Christ, which aroused so much opposition, as the only reasonable attitude. It is mainly for this justification of the worship of Christ that Justin employs the Logos-idea, though where he explicitly deals with the divinity of the Redeemer and his relation to the Father, he makes use of the Old Testament, not of the Logos-idea, which thus can not be said to form an essential part of his Christology.
**On the other hand, Justin sees the Logos as a separate being from God and subordinate to him:
“For next to God, we worship and love the Logos who is out of the unbegotten and ineffable God, since also He became man for our sakes, that, becoming a partaker of our sufferings, He might also bring us healing” (Second Apology, 13).
"There is, and that there is said to be, another God and Lord subject to the Maker of all things who is also called an Angel, because He announces to men whatsoever the Maker of all things, above whom there is no other God, wishes to announce to them… I shall endeavour to persuade you, that He who is said to have appeared to Abraham, and to Jacob, and to Moses, and who is called God, is distinct from Him who made all things, I mean numerically, not in will. (Dialogue with Trypho, 56).
Justin speaks of the divine Logos as “another God” beside the Father, qualified by the gloss: ‘other, I mean, in number, not in will’. Justin actually finds fault with the view of hellenized Jews who held that the divine Logos is no more distinct from God than sunlight is from the sun and suggested, instead, that the Logos is more like a torch lit from another. He wanted to do justice to the independence of the Logos.**
The importance which he attaches to the evidence of prophecy shows his estimate of the Old Testament Scriptures, which are to Christians absolutely the word of God, spoken by the Holy Ghost, and confirmed by the fulfillment of the prophecies. Not less divine, however, is the teaching of the apostles, which is read in the assembly every Lord’s Day—though he can not use this in his “Dialogue” as he uses the Old Testament. The word of the apostles is the teaching of the Divine Logos, and reproduces the sayings of Christ authentically. As a rule he uses the synoptic Gospels – Matthew, Mark, and Luke – but has a few unmistakable references to John. He quotes the Book of Revelation as inspired because prophetic, naming its author. The opposition of Marcion prepares us for an attitude toward the Pauline epistles corresponding to that of the later Church. Distinct references are found to Romans, 1 Corinthians, Galatians, Ephesians, Colossians, and 2 Thessalonians, and possible ones to Philippians, Titus, and 1 Timothy. It seems likely that he also knew Hebrews and 1 John. The apologetic character of Justin’s habit of thought appears again in the Acts of his martyrdom (ASB, Apr., ii. 108 sqq.; Thierry Ruinart, Acta martyrum, Regensburg, 1859, 105 sqq.), the genuineness of which is attested by internal evidence.