In his panegyric oration on Antioch, Libanius tells us that he has delivered more orations and declamations “than anyone”. The extent of his surviving work tends to bear this out. He was very popular as a stylist during the Byzantine period, and more than 250 manuscripts of his collection of letters (or portions of it) survive. The three best copies date from the 11th century: Vaticanus gr. 83 (V), the most complete of the three, Vaticanus gr. 85 (Va) and Leidensis Vossianus gr. 77 (Vo).
1544 letters have reached us, all composed between 355-365, and 388-393. The gap in the middle marks the reign of Valens, whose suspicions of everyone made it too dangerous, most likely, for Libanius as a pagan and friend of Julian to preserve copies of his correspondence. The rate of survival is one letter every three days for that period! Nor were these casual compositions — many were written to be read out.
But much that Libanius wrote is unreadable today. Partly this is because his rhetorical style is out of fashion, and the personal details that might allow us to use his letters as a window onto his life, or the historical details that would make the orations and declamations of historical interest, are few and allusive. Since I bought two TTH volumes at the conference last week, I have been unable to read into them. Indeed I have resorted to the last ploy of the desperate — leaving a copy of the selected letters in the bathroom, to read while washing my hands!
The critical edition of Libanius’ works is that by R. Foerster in the Teubner series, between 1903 and 1927, in 12 volumes. I have been able to find some of these on Google books, and a few more on Archive.org. I have vols.1-7, 9 and 10. The others I could not locate, although they should be out of copyright.
There is a two volume Loeb edition of his autobiography and selected letters, by the late A. F. Norman, but this I have not seen.