Pistis Sophia is a revelation dialogue and it is a long one. Its setting is the risen Jesus remaining with the disciples for eleven years after the resurrection, teaching them, and the bulk of the text is his answers to their questions, with Mary Magdalene asking more of them than anyone else and receiving explicit praise for her understanding.
Its central narrative is the fall and restoration of Sophia, a divine figure who through error descends from her proper place, is oppressed by the archons, and utters a sequence of repentances from which she is progressively raised. Those repentances are given in full and are followed each time by a disciple interpreting them through a psalm, so a considerable part of the book is exegesis of the Psalms placed in the disciples' mouths.
The rest is a mapping of the invisible world in great detail, with names, ranks and the specific mysteries needed to pass each station after death, and a long treatment of the fate of souls that is unsparing.
The manuscript, the Askew Codex, was bought by the British Museum in the eighteenth century and was for a long time almost the only substantial gnostic text available in the original rather than in the words of its opponents.