It is not for me to say whether the Book of Enoch should be canonical or not or whether it is a "real" account or not, but I will say that one of my favorite Old Testament scholars, Dr James Kugel, holds it is great esteem--referring to it as part of the ancient Jewish writings along with the Books of Jubilees and Jasher.
FWIW, Dr Kugel believes the nephilim are indeed the offspring of human women and fallen angels.
"Kugel is Professor Emeritus in the Bible Department at Bar Ilan University in Israel and the Harry M. Starr Professor Emeritus of Classical and Modern Hebrew Literature at Harvard University."
Sounds like a smart cookie.