Aulus Gellius, Attic Nights 7.17
17: Who was the first of all to provide books for the public to read; and what quantity of books were in Athenian public libraries before the Persian invasions?
Pisistratus the tyrant is said to have been the first to make books of liberal disciplines available to be read publicly in Athens. Afterwards, the Athenians themselves increased the collection eagerly and carefully. But later when Xerxes became master of Athens and the city was burned except for the citadel, he stole the entire collection and took it to Persia. Many years later, King Seleucus, who was nicknamed Nicanor, made sure that all of these books were returned to Athens.
At a later date, a great number of books—nearly seven hundred thousand volumes, were either collected or published in Egypt under the Ptolemaic kings; but these books were all burned in our first Alexandrian War during the sack of the city—this wasn’t done on purpose or by any orders, but accidentally by the auxiliary regiment.”
XVII. Quis omnium primus libros publice praebuerit legendos; quantusque numerus fuerit Athenis ante clades Persicas librorum in bibliothecis publicorum.
1 Libros Athenis disciplinarum liberalium publice ad legendum praebendos primus posuisse dicitur Pisistratus tyrannus. Deinceps studiosius accuratiusque ipsi Athenienses auxerunt; sed omnem illam postea librorum copiam Xerxes Athenarum potitus urbe ipsa praeter arcem incensa abstulit asportavitque in Persas. 2 Eos porro libros universos multis post tempestatibus Seleucus rex, qui Nicanor appellatus est, referendos Athenas curavit. 3 Ingens postea numerus librorum in Aegypto ab Ptolemaeis regibus vel conquisitus vel confectus est ad milia ferme voluminum septingenta; sed ea omnia bello priore Alexandrino, dum diripitur ea civitas, non sponte neque opera consulta, sed a militibus forte auxiliaris incensa sunt.
[the War mentioned here is likely 48 CBE; the Library at Alexandria was rebuilt by 41 BCE. It was burned again in 272 CE and abandoned by the end of the 4th century CE]