Among the fragments found at Qumran — the site of the Dead Sea Scrolls — were pieces of a text not previously known to scholars: the Book of Giants. It was found in multiple copies, confirming it was an important text for the community. And it describes events directly connected to the Book of Enoch: the activities of the Nephilim before the flood.
The Book of Giants focuses on the giant offspring of the fallen Watchers — Enoch's giant descendants — and their experience in the days leading up to the flood. Two of the giants, Ohya and Hahya (sons of Shemihaza, the Watcher leader), have apocalyptic dreams that they can't interpret. They bring the dreams to their father. He can't interpret them either. Eventually they send a message to Enoch, asking him to interpret the dreams for them.
Enoch's response, preserved in fragments, seems to have told the giants what the dreams meant: judgment was coming. The flood was coming. Their doom was sealed.
The Book of Giants was later adapted by the Manichaean religion — the religious movement founded by the prophet Mani in the 3rd century CE — as one of their central scriptures. The Manichaean version preserved more of the text, and fragments have been found in multiple languages including Middle Persian, Parthian, and Sogdian.
The Book of Giants isn't included in our collector's edition of the Book of Enoch, but understanding it helps you read Enoch more richly. It confirms that ancient readers found the Enochic tradition compelling enough to expand and develop, and that the stories of the Watchers and Nephilim were living mythology, not dusty theology.