The Book of Enoch, also known as 1 Enoch, is an ancient Jewish religious work ascribed to Enoch, the great-grandfather of Noah. It's not part of the biblical canon used by Jews, apart from Beta Israel (Ethiopian Jews), and it's not included in the Christian Bible, except in the Ethiopian Orthodox Church. It's divided into several key sections which focus on different topics and themes.
The Book of the Watchers (1 Enoch 1-36): This section describes how a group of heavenly beings, known as the Watchers, fell from grace. They descended on earth to marry human women, teaching them forbidden knowledge. Their offspring were the Nephilim, giants who caused destruction and havoc. Enoch is called upon to deliver judgement to the Watchers and the fallen angels.
The Book of Parables (1 Enoch 37-71): This part contains three parables that prophesy the coming judgement of the wicked, the return of righteousness, and the arrival of a messianic figure known as "The Son of Man". Enoch journeys through Heaven and Earth and meets various angelic beings.
The Astronomical Book (1 Enoch 72-82): This book describes a revelation given to Enoch about the movements of heavenly bodies and the calendar, presented through angelic guides.
The Book of Dream Visions (1 Enoch 83-90): Enoch has two visions in this section, one of the Flood, which is a future event for him, and one which describes the history of Israel up to his present day, represented as animals in a metaphorical history.
The Epistle of Enoch (1 Enoch 91-107): This is the final section of the book, including moral exhortations to his children. It contains visions of a future apocalyptic judgement and the rewards of the righteous.
It's worth noting that the Book of Enoch is rich in symbolism and apocalyptic imagery. Some scholars also suggest it may have influenced certain New Testament writers.