Read straight through, the text lurches. A sentence on baptism is followed by a remark about the meaning of a foreign word, then a short parable, then a flat doctrinal assertion, with nothing joining them. The standard explanation is that the work is not a composition at all but a florilegium, a set of extracts copied out of one or more longer treatises, whose compiler kept the sayings and discarded the argument that once held them together. On that reading the incoherence is not a failure of the author but a fact about how the book was made. A minority of scholars still argue for a single designed discourse with an associative rather than linear logic, and the question is not settled.
The material behind the extracts is Valentinian. Valentinus was an Alexandrian teacher active in Rome around the middle of the second century; Tertullian, a hostile witness, says he was passed over for the bishopric there and turned against the church in consequence. The school that carried his name produced the most intellectually ambitious Christian theology of its period, built on a fullness of divine beings, a fall within that fullness, and a redemption understood as the recovery of what had been lost from it.
Much of the book is preoccupied with words. It argues that names given in the world are unreliable, that terms such as God, Father, Son and Spirit deceive those who hear them in their ordinary sense, and that truth had to be spoken in worldly language because there was no other way to reach people who live in the world. That suspicion of religious vocabulary, held by a text that is itself nothing but vocabulary, is the closest thing the collection has to a governing idea.