[Why is hell eternal? Why can't people be just annihilated? Most of the answers I heard sound like just a plain cope.]
It's the words of Yaldaboath, the Demiurge, who is vengeful and cruel. He wants man to fear him. Our bodies die but the light within us that can comprehend the immortal forms lives on. We must become purified of the material world or else we will be reborn into it. The Hindi idea of Atman is useful here. Our Atma is trapped in the realm of the Demiurge and his Archons until we attain Knowledge (Gnosis) of God and the eternal forms.
The Bible has become corrupted by man. Read the Apocryphon of John and the Hypostasis of the Archons for a full version of Genesis. Books of the Bible are still worth study, particularly Proverbs, Ecclesiastes, and th Gospel of John. The Gospel of Thomas contains the original quotes for Mark and Luke but also quotes that were censored. The Foreigner, Thunder, and Zostrionos all contain Wisdom.
As important is the Wisdom of the sages. The complete works of Plato and surviving Parmenedies and Heraclitus are as useful, or moreso, than much of the Bible.
In terms of modern work, Whitehead and Pierce's semiology are great additions to a Canon.