Book of Enoch, BTW, is a borderline work. Some Church Fathers considered it to be part of Sacred Scripture, and the Epistle of St. Jude appears to quote it directly.
But, since the Church did not ultimately accept it as part of the Canon of Sacred Scripture, there's often a false dichotomy engaged where people conclude that it's fraudulent, some kind of fictional gnostic fabrication, like some things were.
People need to keep in mind, however, that just because something is not INSPIRED by the Holy Ghost, this does not mean it cannot be authentic, real, and genuine. It could in fact have been written even by Enoch himself, at least in substance ... just that he wasn't inspired when he wrote it. I'm sure St. Paul wrote other stuff than what appears in the New Testament that wasn't inspired, and the mere fact that St. Paul wrote something doesn't make it inspired. Inspiration is not some kind of habitual gift where once an author is inspired, everything that comes off his pen is written by the Holy Ghost.