Jude is basically talking of "A" prophecy of Enoch....not the "Book".
Well. Judes prophecy was taken from the book of Enoch. The same book found intact by Charles bruce in 1800's Ethiopia.
Compare please.
Jude.... 14And Enoch also, the seventh from Adam, prophesied of these, saying, Behold, the Lord cometh with ten thousands of his saints,
15To execute judgment upon all, and to convince all that are ungodly among them of all their ungodly deeds which they have ungodly committed, and of all their hard speeches which ungodly sinners have spoken against him.
Enoch...Chapter 2, verse 1...Behold, he comes with ten thousands of his saints, to execute judgment upon them, and destroy the wicked, and reprove all the carnal for everything which the sinful and ungodly have done, and committed against him.
Pretty clear to me.