To the Gnostics, the God of the Old Testament is evil (and named Yaltabaoth), thus evil is God's deliberate creation. Likewise Eve becomes a heroic figure trying to find the knowledge of truth (by consuming from the Tree of the Knowledge of Good and Evil) which the evil God did not wish her to find. As such, in Gnostic thought, Eve would have achieved salvation precisely by eating from the tree, in contrast to more orthodox Christianity in which this act was the source of original sin.
The only known content from it are a few quotations by Epiphanius, a church father who criticised how people used it to justify free love, by practicing coitus interruptus and eating semen as a religious act. Although a proportion of the Gnostics held that since the flesh is intrinsically evil, one should acknowledge that one is aware of this by committing extreme carnal acts, the majority of the Gnostics took the opposite view of extreme asceticism, and Epiphanius may just be inventing propaganda.
Gnostics typically wrote on multiple levels, imbuing texts with complicated mystical esoteric meaning, rather than intending a base interpretation. It is possible that Epiphanius failed to realise this and only read into the text a simple literal interpretation; the quotation Epiphanius claims is a reference to semen is
This looks like the beginning. The reference to the 'tall man' might be to Jesus, and to the 'other of short stature' is suggestive of Mary. The reference to thunder is curious. The man speaks but this is the voice of Eve. See also The Thunder, Perfect Mind