Read 1 Enoch and 2 Enoch, both pieces of 2nd Temple Jewish literature found in the dead sea scrolls that are also heavily drawn on by many of the New Testament writers (Jude, 1 & 2 Peter, etc). You can usually find them in weird compilation books with whacky titles like “The Lost Books of the Bible,” etc. If not email me privately and I can send you a word document attached with 1 Enoch copied and pasted. Besides a retelling of Genesis, it covers how the “sons of God” in Genesis 6 were interpreted to be fallen angels. Interestingly, the fallen angels that impregnated human women and gave them “secret knowledge” were imprisoned immediately in the pit, whereas demons were understood to specifically be the spirits of their giant offspring that were released after the death of the giant’s body. This interpretation was most popular with Jews of the second Temple period, as well as the first few centuries of Christians before being abandoned in favor of the “sethite view.”
The giants ask Enoch to beg for mercy on their behalf, Enoch gets a tour of the underworld (which has parallels with the parable of the rich man and Lazarus), and has some rich visual imagery throughout. As apocalyptic works go, it’s a fun read.