How then would the person who referenced Enoch have known if there were no books written? This is thousands of years ago. Do you believe that what was referenced was handed down orally for those many years?[/QUOTE]
How did Moses know that in the Beginning God created the Heavens & the earth? How did Moses know about the Tower of Babel or Noah?
How did Eiljah know the plans of the King of Syria, so Elijah could report them to Ahab?
How did Matthew (27) know that Jeremiah uttered this prophecy?:
"Then was fulfilled that which was spoken through Jeremiah the prophet, saying, And they took the thirty pieces of silver, the price of him that was priced, whom certain of the children of Israel did price; and they gave them for the potter’s field, as the Lord appointed me."
There is no such prophecy in the Book of Jeremiah.
Pasa graphē theopneustos (all scripture is God-outbreathed).
"And we have the word of prophecy made more sure; whereunto ye do well that ye take heed, as unto a lamp shining in a dark place, until the day dawn, and the day-star arise in your hearts: knowing this first, that no prophecy of scripture is of private interpretation. For no prophecy ever came by the will of man: but men spake from God, being moved by the Holy Spirit."
Jude was a prophet giving the Word of God. God was around when Enoch prophesied.
I don't know of anyone (aside from obsurantists) who thinks that Enoch wrote a book and it was extant at the time of Jude. The prophets gave oral prophecy. It was not all recorded and put in books. But the Lord knows what He produced via their mouths. And the Lord wrote the book of Jude.
So the Lord tells us in Jude what Enoch prophesied. I can see an enterprising fellow concocting a Book of Enoch off that.