Publication was slow, and the delay was not accidental. One codex was taken out of Egypt and bought in 1952 for the Jung Institute in Zurich, becoming the Jung Codex; its leaves were returned to Cairo only in 1975, and the arrangement soured relations for years. The Egyptian material was tied up by the Suez crisis and the 1967 war, and by a small circle of scholars who held exclusive publication rights and released little. Two decades after the discovery, most of the collection remained unavailable to anyone outside that circle.
James Robinson broke the impasse by assembling an international team under UNESCO auspices and forcing the material into the open. A complete facsimile edition appeared from Brill through the 1970s and early 1980s, so that anyone could work from photographs of the pages, and a one-volume English translation, The Nag Hammadi Library in English, was published in 1977. Everything written about these texts for a general readership dates from after that.
What the find changed is easy to state. Before it, the movements were known almost entirely through Irenaeus, Hippolytus and Epiphanius, opponents summarising in order to refute. Reading the texts directly showed those writers to have been more reliable than expected in places, since Irenaeus's summary of the Apocryphon of John is recognisably accurate, and much less reliable elsewhere, since the sources turned out to be more varied, more Christian and less uniformly contemptuous of the body than the polemic suggested. The category itself came under pressure. Michael Williams and Karen King have argued that Gnosticism, as a single religion with a common creed, is a modern construct assembled from the heresiologists rather than a thing the texts describe, and that it is better to speak of particular systems, Valentinian, Sethian, Thomasine, and say what each one actually holds.