The Gospel of Truth opens by naming itself good news for those who have received grace to know the Father, then spends most of its length describing what not knowing him is like. Error is pictured as a fog that thickened around the world in place of truth, and as a nightmare people mistake for waking life, full of terrors and phantoms and flight, until the one having the nightmare wakes and finds there was nothing there. The world itself is said to have come from that forgetting rather than from a deliberate act of the Father, and it is oblivion, not matter, that the text treats as the real problem.
Against this it sets the Word, sent to give shape to the ignorance and swallow it up, and knowledge of the Father as what actually reverses the forgetting. Those who receive this knowledge are not merely informed of a fact; they are called by name, the way a father calls a child he already knows, and the text says plainly that a name is given to a thing that already exists rather than invented for it. The redeemed are pictured resting in the Father the way exhausted people rest, and the closing image is of a household set in order, each thing restored to the place from which it had strayed.
There is no cosmogonic myth of aeons falling and being restored, no demiurge, and no elaborate genealogy of divine emanations of the kind Irenaeus attacks at length elsewhere in his account of Valentinian teaching. What the text offers instead is closer to spiritual instruction than to myth, which is part of why calling it Gnostic tells a reader less than reading what it actually says.