You raise a good question about canonicity, which is a touchy and rather discretionary topic and one which is, in my opinion, blown out of proportion. Catholics point to texts like Tobit and 2 Maccabees and claim that current Catholic customs are evident in the text. Read Scott Hahn’s “Signs of Life” for more on this. However, other than that, and other than a few daily lectionary readings, the texts are hardly ever touched. Not that the texts are worthless. On the contrary, deutero- and non-canonical texts only serve to enlighten us about the New Testament.
Consider 1 Enoch, which the Letter of Jude cites. One of the central figures featured in this text is a transcendent heavely being who is called variously “the Son of Man,” “the Chosen One,” “the Righteous One,” and “the Anointed One.” These titles and the manner in which the author depicts this figure indicate that this heavenly being is the embodiment of four characters in biblical literature: the “one like a son of man” in Daniel 7:13-14; the Servant of the Lord in Isaiah (52:13-53:12); the Anointed One of the Lord found in the Psalms and Proberbs; and heavenly Wisdom in Proverbs 8, who existed before creation. All of these titles were later bestowed upon Jesus, likely due to the fact that members from the community which composed 1 Enoch joined the early Christian movement and, combined with their knowledge of the Synoptics and John, relayed their tradition concerning a pre-existent, heavenly being who would come to Earth as a human being, correct humanity’s corrupt, sinful ways, then suffer and die for the sins of mankind. It’s remarklable, then, isn’t it, that even though the Church still interprets the above prophetic passages as referring to Jesus, 1 Enoch, once regarded as Sacred Scripture by some of the early Church Fathers, did not find its way into the canon?
Again, the canon is a highly discretionary topic. I recommend purchasing a Bible with the full Apocrypha. As I said above, deutero- and non-canonical texts only serve to enlighten us about the world of the New Testament.