"If the book trade had come to stay, then the commercial copying and selling of texts did not replace their private reproduction and circulation, in Rome or elsewhere. . . . [an] interesting papyrus letter (P. Oxy.2192) alludes to private efforts to obtain texts in Egypt in the late second century. That letter carries a postscript in the hand of the sender that reads: 'Make and send to me copies of books 6 and 7 of Hypsicrates' Characters in Comedy. For Harpocration says that they are among Polion's books. But it is likely that others, too, have got them. He also has prose epitomes of Thersagorus' work on the myths of tragedy.' Here the writer asks his correspondent to make copies of books that he wants and suggests an individual who owns them who might permit them to be copied. Following this postscript is a note written in a different hand. It reads: 'According to Harpocration, Demetrius the bookseller has got them. I have instructed Apollonides to send me certain of my own books, which you will hear of in good time from Seleucus himself. If you find any, apart from those I possess, make copies and send them to me. Diodorus and his friends also have some which I haven't got.' It is not certain who appended this note; it was probably added by a member of the letter writer's circle as a supplement to the preceding postscript. The letter reveals a group of friends who acquired books by making copies from exemplars owned by friends who lived elsewhere (Harpocration, Polion, Diodorus, and their circle). Yet there is mention of the bookseller Demetrius, who could serve as a fall-back source. Here, then, in provincial Egypt we see the independent coexistence of private and commercial means of obtaining books.
"We know that some of individuals named in this letter--Harpocration, Polion (Pollio), and Diodorus--were professional scholars, known for their lexigraphical work. The books requested are scholarly, not books that have popular appeal, so it is surprising that the bookseller Demetrius might have them. One would expect a bookseller to deal in popular literature, as apparently was the case with the Roman booksellers we know by name. In a setting where a scholarly community was active, an astute dealer probably did not disdain service to that clientele. Yet, as a rule, classical texts and especially scholarly tools and studies circulated principally if not exclusively through private channels. The practices of Cicero in late republican Rome, of the scholarly circle in Oxyrhynchus in the late second century, and of Libanius and his fellow scholars in fourth-century Syrian Antioch, widespread as these were in time and place, all attest that private copying and circulation formed the persistent norm for professional scholars.
"The reason for this was not only the limited market for scholarly works. The quality of commercial copying was not particularly high, whereas scholars were fastidious, at least about their books. The complaints voiced by many ancient writers about the quality of commercial copies were consistent and continuous. The employment of mediocre copyists and the failure to collate copies and exemplars--practices that Strabo (13.1.54) encountered in Alexandria as well as Rome--resulted in books that did not meet the scholarly standard" (Gamble, Books and Readers in the Early Church. A History of Early Christian Texts  92-93.)
Turner, Greek Manuscripts of the Ancient World (1971) no. 68 (p. 114) reproduces the text and an excellent black and white image of P. Oxy.2192.