Was silent reading unusual during Augustine's time? If so, what implications might a comment by Augustine in his Confessions (6.3.3.) have on the larger question of whether reading was primarily oral rather than silent in the ancient world?
In "Toward a Sociology of Reading in Classical Antiquity," American Journal of Philology 121 (2000) 593-627 William A. Johnson quoted Augustine's passage from the Confessions concerning the reading habits of his mentor, the archbishop of Milan, Aurelius Ambrosius, who read silently. The inference is that silent reading was unusual in Augustine's time:
"When Ambrose read, his eyes ran over the columns of writing and his heart searched out the meaning, but his voice and his tongue were at rest. Often when I was present—for he did not close his door to anyone and it was customary to come in unannounced—I have seen him reading silently, never in fact otherwise. I would sit for a long time in silence, not daring to disturb someone so deep in thought, and then go on my way. I asked myself why he read in this way. Was it that he did not wish to be interrupted in those rare moments he found to refresh his mind and rest from the tumult of others' affairs? Or perhaps he was worried that he would have to explain obscurities in the text to some eager listener, or discuss other difficult problems? For he would thereby lose time and be prevented from reading as much as he had planned. But the preservation of his voice, which easily became hoarse, may well have been the true cause of his silent reading."
In A History of Reading (1996) Alberto Manguel devoted Chapter Two to "The Silent Readers." This was one of the most detailed expositions on silent reading, including the issue of how reading aloud was probably the norm since the beginning of the written word. In August 2019 the text of that chapter was online at this link.
In September 2014 I had the pleasure of viewing the German biographical film starring Franco Nero, Des Leben des heiligen Augustinus (2010). Conveniently the DVD was very well dubbed in English. This was best film that I had seen to date with respect not only to its treatment of Augstine's life, but also in its authentic depiction of book rolls and early codices in the period of transition from the roll to the codex. As expected, the trailer in English did not feature the book aspect of Augustine's life.