The history of the Bible is an interesting thing. A collection of stories culled from both the original Torah and writings created later, it is a repository of general scripture that a multitude of branches of Christianity take as sacred. (Some literally, but that’s not the point here.
Certain stories did not make it into the full text, known as the Canon. These are collectively called Apocrypha. Some texts are apocryphal because a) they may have incited heresy (Gospel of Judas), b) were generally disliked by specific people in charge (Song of Solomon, which—let’s face it, is basically the first written erotica), or c) they were just plain weird (Gospel of Thomas anyone?)
The Book of Enoch—or if we’re being really careful about technicalities, 2 Enoch (read as “second Enoch”) is the story of Enoch—the second Enoch if we’re being neurotic still. (I wonder if this was intentional. If not, it’s just weird.) Enoch, an ancestor of Noah, was evidently going about his business when sudden an archangel is like “HEY! LISTEN!” and drags him into something strange. Under the angel’s tutelage he learns the secrets of creation—including the ones that the Watchers, fallen angels, taught humanity against the supreme god’s will.
Stumbling over this fact, one of the Watchers petitions Enoch to act as a go between, trying to be let back into the heavens. It’s back and forth, as Enoch learns more about what is going on and what he has to do. He is forced to be the conduit through which the divine decree—permanent exile—is delivered.
It isn’t an easy message to deliver. In fact it’s such a difficult message to both deliver and take that neither Enoch nor the Archangels take it particularly well—there is a spat between Raphael and Michael, wanting to rush in and beg an alternative decision—ANY alternative but exile.
So yeah, fallen angels beg for mercy, don’t get it, Archangels concur and want to stop it. Not a message that the church would want out there. TO THE APOCRYPHA IT GOES.
There are a few good translations out there. The Book of Enoch is considered an important part of Ethiopian Christianity, though not generally accepted as canon. I recommend it—it is an interesting read, especially for comparative religious study or for metaphysics/mythology buffs.