Hello GandalfTheWhite,
I have a copy of Ethiopic Enoch and find the opposite, that it fills in a lot of the details that the Genesis does not go into, mentions the son of Lamech, Michael, Gabriel, the flood and a host of other related items. It gives a much better understanding of why God flooded the earth. As far as its credibility, if God put Jude's quote of Enoch in His word, then that speaks for itself. The popular understanding of this is that, Satan through those angels attempted to corrupt the blood line in order to interfere with the prophecies regarding the Messiah who would come into the world in the flesh. I have not done my own personal studies on this, so I will not elaborate any further. I would say this, since Jude quoted from the prophecy of Enoch and it is in the word of God, I would not be referring to the prophesies of Enoch as Satanic.