We first learn of Enoch in Genesis 5 but it leaves us with questions. Hebrews 11 has the answers and Jude quotes Enoch! How did Jude come to know the words of Enoch? They are not in the Bible. The answer of course, is The Book of Enoch. A book which is actually quoted not only by Jude, but also James the natural brother of Jesus.
The quote in (Jude 14-15) & (1 Enoch 1:9) is as follows: "In the seventh (generation) from Adam Enoch also prophesied these things, saying: 'Behold, the Lord came with his holy myriads, to execute judgment on all, and to convict all the ungodly of all their ungodly deeds which they have committed in such an ungodly way, and of all the harsh things which ungodly sinners spoke against him'."
What is the Book of Enoch and where did it come from?
Enoch was the grandfather of Noah.
The Book of Enoch chapter 68:1 "And after that my grandfather Enoch gave me all the secrets in the book and in the parables which had been given to him, and he put them together for me in the words of the book of the parables." This makes it possible for the Book to have survived the flood as its not too hard to accept that Noah would have taken his Great Grandfathers writings with him onto the ark.
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. This and many other books became discredited after the Council of Laodicea. And being under ban of the authorities, afterwards it gradually passed out of circulation.
At about the time of the Protestant Reformation, there came to be a renewed interest in the Book of Enoch which had long since been lost to the modern world. By the late 1400's rumors began to spread that somewhere a copy of the long lost Book of Enoch might still exist.
During this time many books arose claiming to be the long lost book and were later found to be forgeries.
The return of the long lost Book of Enoch to the modern western world is credited to the famous explorer James Bruce, who in 1773 returned from six years in Abyssinia with three Ethiopic copies of the lost book. In 1821 Richard Laurence published the first English translation. The famous R.H. Charles edition was published in 1912.
In the following years several portions of the Greek text surfaced. Then with the discovery of cave 4 of the Dead Sea Scrolls, seven fragmentary copies of the Aramaic text were discovered.
The Book of Enoch is divided into five basic parts, but it is the The Book of Parables (37-71) which gives scholars the most trouble for it is primarily concerned with a figure called "the messiah"; "the righteous one"; "the chosen one" and "the son of man."
Chapter 46:1-2  There I beheld the Ancient of days whose head was like white wool, and with him another, whose countenance resembled that of a man.
His countenance was full of grace, like that of one of the holy angels. Then I inquired of one of the angels, who went with me, and who showed me every secret thing, concerning this Son of man; who he was; whence he was; and why he accompanied the Ancient of days.  He answered and said to me, This is the Son of man, to whom righteousness belongs; with whom righteousness has dwealt; and who will reveal all the treasures of that which is concealed: for the Lord of spirits has chosen him; and his portion has surpassed all before the Lord of spirits in everlasting uprightness."
The opening verses of the Book of Enoch tell us that the revelations in this book were not meant for Enoch's generation, rather a remote generation, and of course the book would make more sense to the generations after Christ.
We know that the early Church made use of the Book of Enoch, but it was then all but lost, until recent times. Perhaps this book was meant for our generation, as it is widely available today after being concealed for over a millennia.
(Enoch 1:1-3) The words of the blessing of Enoch, wherewith he blessed the elect and righteous, who will be living in the day of tribulation, when all the wicked and godless are to be removed. And he took up his parable and said -Enoch a righteous man, whose eyes were opened by God, saw the vision of the Holy One in the heavens, which the angels showed me, and from them I heard everything, and from them I understood as I saw, but not for this generation, but for a remote one which is for to come.