In the third chapter of this book, Greenblatt relates an anecdote which it has taken me ages to track down;
By the first century CE there were distinctive signs of the emergence of what we think of as a “literary culture.” At the games in the Colosseum one day, the historian Tacitus had a conversation on literature with a perfect stranger who turned out to have read his works. Culture was no longer located in close-knit circles of friends and acquaintances; Tacitus was encountering his “public” in the form of someone who had bought his book at a stall in the Forum or read it in a library. This broad commitment to reading, with its roots in the everyday lives of the Roman elite over many generations, explains why a pleasure palace like the Villa of the Papyri had a well-stocked library.
Looking at the print edition, I notice that he does include an endnote; 63 At the games in the Colosseum: Erich Auerbach, Literary Language and Its Public in Late Latin Antiquity and in the Middle Ages, trans. Ralph Manheim (Princeton: Princeton University Press, 1965), p. 237.
I didn't look up that citation (one of the pitfalls of preferring audiobooks), but I did finally find the ancient source of this anecdote, which appears in the letters of Pliny the Younger, book 9, letter 23 (To Maximus);
When I have been pleading, it has often happened that the centumviri, after strictly preserving for a long time their judicial dignity and gravity, have suddenly leaped to their feet en masse and applauded me, as if they could not help themselves but were obliged to do so. I have often again left the senate-house with just as much glory as I had hoped to obtain, but I never felt greater gratification than I did a little while ago at something which Cornelius Tacitus told me in conversation. He said that he was sitting by the side of a certain individual at the last Circensian games, and that, after they had had a long and learned talk on a variety of subjects, his acquaintance said to him:
"Are you from Italy or the provinces?" Tacitus replied:
"You know me quite well, and that from the books of mine you have read."
"Then," said the man, "you are either Tacitus or Pliny."
I cannot express to you how pleased I am that our names are, so to speak, the property of literature, that they are literary titles rather than the names of two men, and that both of us are familiar by our writings to persons who would otherwise know nothing of us. A similar incident happened a day or two before. That excellent man, Fadius Rufinus, was dining with me on the same couch, and next above him was a fellow-townsman of his who had just that day come to town for the first time. Rufinus, pointing me out to this man, said, "Do you see my friend here?" Then they spoke at length about my literary work, and the stranger remarked, "Surely, he is Pliny." I don't mind confessing that I think I am well repaid for my work, and if Demosthenes was justified in being pleased when an old woman of Attica recognised him with the words, "Why, here is Demosthenes,"1 ought not I too to be glad that my name is so widely known? As a matter of fact, I am glad and I say so, for I am not afraid of being considered boastful, when it is not my opinion about myself but that of others which I put forward, and especially when you are my confidant - you who grudge no one his fair praise, and are constantly doing what you can to increase my fame. Farewell.
1See Cicero, Tusc. v. (36)103.