I think that the Bible will often time draw from other sources, either explicitly by referencing those other sources, or by using similar quotations, as you would find in other books. For example, there are judgement metaphors in the Book of Revelation, which you find in1st century literature. Those judgment metaphors, therefore, have an understanding in the 1st century that you can derive from 1st century literature. But, of course, that does not mean that the 1st century literature is inspired literature.
I think that same principle applies, if you look at the Book of Jude. Jude mentions Enoch as the seventh from Adam, and mentions that Enoch had prophesied about men that are being described in the Book of Jude (Jude 14ff). Now, Jude was well respected as was Enoch in New Testament times. So Jude is now, as a well-respected church father or disciple of Jesus Christ, is quoting from the book of Enoch, but his quote does not mean that Enoch is inspired in the sense of supernaturally revealing new truth. Jude simply finds a quotation to be a helpful confirmation of truth that is already well established, and that’s the point.
The Book of Enoch is not inspired literature, but that does not mean it does not have truth. For example, it is true to say, whether this is in the Canon or outside the Canon that “the Lord is coming” or that “false prophets will appear,” or that “the wicked will be judged.” So, these are true statements, regardless of where you find them. But the fact that Enoch is being quoted does not of necessity mean that the quote is from inspired literature. It is a confirmation of truth that is well established.
—Hank Hanegraaff
For further study, see the following:
Is the New Testament Canon Authoritative or Authoritarian? (Hank Hanegraaff)
Gnosticism and the Gnostic Jesus (Douglas Groothuis)
The Gnostic Gospels: Are They Authentic? (Douglas Groothuis)
[Answer taken from “What’s Your Opinion on the Book of Enoch since Jude Quotes from it in His Epistle?” http://www.equip.org/audio/whats-your-opinion-on-the-book-of-enoch-since-jude-quotes-from-it-in-his-epistle/]