My latest read is this volume by Carl B. Smith, No Longer Jews: The Search for Gnostic Origins (2004). There is a review at RBL by Philip Tite. The contention of Smith is:
“My contention in this book is that evidence regarding the religious intellectual milieu, geographical context, and chronological sequence of clearly gnostic teachers and documents point to an early second-century rise of the gnostic religion in the Jewish intellectual centers of North Africa. The crisis out of which Gnosticism arose was not that of the Jewish revolts of Judea; rather, it was the lesser-known revolt that originated in Cyrenaica and Egypt in 115-117 C.E. during the reign of the Roman emperor Trajan.” (p,4)
“It is entirely possible that Hellenistic Jews responding to the disappointment of the revolt, Jewish Christians uniquely impacted by the disaster, and/or Gentiles intimately acquainted with Judaism and seeking out to distance themselves from it, forged the gnostic system out of the intellectual and religious ruins of this event.” (p,4).
There is also a list of the salient aspects of Gnosticism from Birger Pearson (Gnosticism, Judaism, and Egytpian Christianity [Minneapolis: Fortress, 1990], 7-9) on pages 11-12:
• Gnosis. It was gnosis rather than faith or law that were the requisites to salvation.
• Theology. There is a transcendent supreme God over the god or powers responsible for the world in which we live.
• Cosmology. The world was created by a lower god/power inferior to the supreme God and the world is a prison of human souls.
• Anthropology. Human beings are constituted by inner self, divine spark, that originated in the transcendent divine world and by means of gnosis can be released from the cosmic prison and return to its heavenly origin.
• Eschatology. The eventual salvation of the elect from the material world via gnosis.
• Social. Gnostics founded communities and were not wholly individualistic.
• Ritual. Gnosticis had their own religious ceremonies.
• Ethical. Asceticism and withdrawal from sex and procreation.
• Experimental. Joy in the salvation won by gnosis.
• Myth. Elaborate myths of cosmic creation.
• Parasitical. It borrows from other systems of belief.
For another good summary of gnosticism see Bart Ehrman, Jesus: Apocalyptic Prophet of the New Millenium, pp. 74-75. Available on Amazon for a full search. Search under gnosticism on the . Amazon webpage