I'm pretty familiar with it - and you're quite right. I think there's a divorce between formal religious beliefs and those held by the majority of people. The Hebrews and Jews of the time would have been incredibly familiar with the Book of Enoch, but the formal religious leaders considered the writings heretical. It didn't change their influence.The Book of Enoch was considered 'heretical' as it posited the 'Watchers' as 'divine beings'. The other books were 'intertestamental literature' and used for historical reference, but not authoritatively in the way the canonized Books were. Since the Hebrews didn't canonize them, neither did Christians.
I think the same is true today, many popular religious concepts and beliefs are looked down upon by formal religious bodies. Black theology in the West is centered on a mix of pre-Christian superstitions and Baptist/Methodist/Episcopal teachings.
You're just as likely to hear quotes from MLK Jr. and the Book of Common Prayer as you are to hear the Sermon on the Mount.

