In the ancient world, texts are written for the ear, not for the eye.
The Iliad repeats whole blocks of speech that are relayed from agent to agent to agent, with only the most minor modifications; these repetitions of large chunks of text are often irritating for us modern readers (“why not simply say, ‘and what Zeus said was repeated’, or something?” children I tutor have asked me), but they are a part of oral culture, not meant to be read with the eye, but heard with the ear, sung by a bard, not seen by a solitary reader — and the memories of people in an oral culture have a different capacity and life than our memories do. Poetry in this world functions, in part, as a servant to memory. (I have written about this partly here, and again here.)
I am working through Plato’s Republic with a friend who had never read it, and he laughed with delight and exclaimed at the end of our last session: “I need to say that I would not have gotten this much out of it had I read it on my own; this is waaaay better!” The benefit of reading a Platonic dialogue aloud in a group together, taking different characters in turn, is probably a built-in expectation; the dialogue format is not for private reading, but for performance among friends, and only there can it serve as a mirror, or the proxy of the mirror that a real dialectic acts as for the soul. The texture of the characters and the arguments must be heard and even performed, rather than simply read, to be grasped, to be learned. Even the Platonic work of Euclid is meant to be heard, so that its exercises can be performed — I presume in the context of a school. In Porphyry’s Life of Plotinus, it seems that arguments are read aloud by members of Plotinus’ circle on the birthdays of Plato and Socrates.
The continuous script of Codex Vaticanus (example in header) and one of my student’s comments on seeing an image from it: “how do you read that, how do you clearly see the words?” It is not meant to be seen, but to be heard; the words are first learned by hearing them as children, and these words, from this text, are practiced in this form by a reader for an audience; the text is not meant primarily to be scanned with the eyes, but heard; even those who were highly literate in the Greco-Roman world would be read to as often as they would read to others (so says Gamble), and as we know from the amazement that St. Augustine expressed at his discovery that St. Ambrose was reading silently, this practice of reading silently can be dated — and if memory serves, St. Ambrose’s were not even moving, though Augustine still assumed that, were he to get close enough, he would be able to hear — because everyone moved their lips and activated their voice when speaking, even if but a little. (To this end, this page looks interesting.)
As far as I understand it, widespread literacy is a Protestant innovation within the modern period, predicated on the idea that every good Christian must be able to read the Bible privately. The Bible would never have been encountered this way in the ancient world, nor would much of anything have been — not with an estimated 10% literacy rate, where things were read aloud on numerous occasions, and memories were much better than they are today.
Whether a novel for the cultured, or a work of high poetry, or epic, or verse, or Biblical (canonical or non-canonical; the Christian pot was both bigger and smaller before Origen and then Athanasius, and continued to be somewhat fuzzy in many places long after), both the literate and the illiterate would have plenty of occasions to hear, remember, memorize, and absorb even the most elite literature, Pagan or Jewish or Christian.
Header image is from Codex Vaticanus, which can be found online. Google it. I dare you.