The haul is conventionally counted as thirteen codices: twelve substantially intact books plus the loose leaves of a thirteenth, tucked inside another cover. Between them they carry fifty-two tracts, with some duplication, and around forty of the works were entirely unknown before 1945. Not all are Christian. Three pieces belong to the Hermetic literature, and one is a clumsy Coptic rendering of a passage of Plato's Republic that the translator appears not to have understood.
The books can be dated with unusual precision because of their bindings. The leather covers were stiffened with cartonnage, waste papyrus pasted into layers, and that waste included dated documents: letters, receipts and accounts from the middle decades of the fourth century. The codices were therefore manufactured no earlier than that. The texts they carry are older, in some cases much older, being Coptic translations of Greek works whose composition ranges from the second century to the fourth.
Why they were buried is inference, not record. The cartonnage includes material with monastic connections, and one of the great Pachomian monasteries stood a few miles away. The most frequently offered explanation is that monks owned the books and concealed them after Athanasius of Alexandria, in his festal letter of 367, listed the acceptable scriptures and condemned the reading of apocryphal writings. It is a plausible reconstruction that fits the dates and the geography. It is not proven, and scholars who work on the cartonnage disagree about how firmly it ties the codices to the monastery.