1. The book of First Enoch was part of the Dead Sea Scrolls Bible - the Essene Library of Qumran in Israel. First Enoch was included amongst the Dead Sea Scrolls, in fact was one of the most widely read holy books at Qumran (400 bc - 70 ad). This is based upon the large number of Enoch fragments found there. Many Jews were using Enoch before and during the time of Jesus. Here's a photo of a page of First Enoch from the Dead Sea Scroll discovery.
   
   
2. Because it was so popular, highly respected and influential, it's no surprise then to discover that the author of the New Testament book of Jude quoted First Enoch. Jude quoted Enoch in verses 14 & 15 of his New Testament epistle (letter), a great canonical indorsement for Enoch. The quote in Jude, verses 14-15, is from, First Enoch, Chapter One, Verse Nine. The Bible that bares the most resemblance to the early church Bible of Jude, is the Ethiopian Bible, as Jude not only quotes from Enoch, but also from another book called, the Assumption of Moses. Both Enoch and the Assumption of Moses are contained in the Ethiopian Bible; see more on the Ethiopian Bible below.
   
   
3. The Early Church father Tertullian used Enoch as sacred scripture. Tertullian quotes a passage from the Book of Enoch, which to him had the value of "Scripture". The Epistle of Jude (verse 14) is also appealed to by Tertullian as a testimonial to the authority of Enoch. (see, De cultu feminarum. 1.3)
   
   Tertullian's canon of the Old Testament included the deuterocanonical books, since he quotes most of them. He also cites the Book of Enoch as inspired, and thinks those who wanted to reject it were wrong. Tertullian.org
   
   "The Book of Enoch was extant centuries before the birth of Christ and yet is considered by many to be more Christian in its theology than Jewish. It was considered scripture by many early Christians. The earliest literature of the so-called "Church Fathers" is filled with references to this mysterious book. The early second century "Epistle of Barnabus" makes much use of the Book of Enoch. Second and Third Century "Church Fathers" like Justin Martyr, Irenaeus, Origin and Clement of Alexandria all make use of the Book of Enoch. Tertullian (160-230 C.E) even called the Book of Enoch "Holy Scripture". The Ethiopic Church even added the Book of Enoch to its official canon. It was widely known and read the first three centuries after Christ": More about Enoch
   
   
4. Barnabas, like some other major leaders of the Early Church, quoted Enoch as scripture, sometimes even using the term "scripture" to describe the Enoch passages he quoted. See, the Epistle of Barnabas, translated in the book Early Christian Writings - The Apostolic Fathers, Maxwell Staniforth, Penguin Classics.
   
   
5. The Ethiopian BIBLE, even now in the modern world, still contains the books of Enoch (and several other surprising books once banned and thought to be forever lost), thus preserving the earlier tradition dating back to the time of the Dead Sea Scrolls and the New Testament which viewed Enoch to be an inspired sacred book.

The Ethiopian Book of Enoch:
Read Enoch Online
Also see:
http://wesley.nnu.edu/biblical_studies/noncanon/ot/pseudo/enoch.htm
http://reluctant-messenger.com/enoch.htm