What do you believe about this book?
Usually people's knee-jerk on this subject is, "its not a part of the canon of my church", or "its not inspired".
I am noting you're not raising those issues.
I'd like to raise an entirely different possibility, not related to canon...
I believe, after having NOT wanted to believe so for some time, the Book of Enoch was written by the Biblical Enoch. Apparently, Jude did too. Not only did Jude quote Enoch 1:9, he in fact alludes the the contents of Enoch's book at least seven times in his tiny epistle. Jude was a veritable Book of Enoch apologist. There's not been many of those on record in the history of Christendom since Jude's time.