Before 1945, our knowledge of Gnostic thought came almost entirely from hostile sources — the heresiologists like Irenaeus and Epiphanius, who quoted Gnostic texts only to refute them. The Nag Hammadi discovery changed everything: for the first time, scholars had direct access to what the Gnostics actually wrote.
The texts above range from systematic cosmological treatises (Secret Book of John) to collections of Jesus's sayings (Gospel of Thomas) to poetic meditations (Thunder, Perfect Mind) to practical afterlife guides (First Apocalypse of James). All are available free online — links provided on each page.