The manuscripts of Mount Athos (Agion Oros)

To the Orthodox, the Holy Mountain is the heart of the Church. It is here that Orthodox monasticism has found its centre since the end of the first millennium, and here that it still lives on in its thousand-year-old traditions. To the monastic, student of monasticism, or general monastic enthusiast, there are few places more interesting and inviting than the Holy Mountain.

'Mount Athos' is the name of the peak that rises 2,033 metres out of the sea at the southernmost point of the northernmost peninsula of Halkidiki in Macedonia, Greece; yet often the entire peninsula is simply called 'Athos'. Officially, its Greek name is Aghion Oros�the Holy Mountain�and as anyone who has studied the Holy Mountain knows, this small piece of land has had a long and interesting history. At one point, Xerxes of Persia dug a canal accross the base of the peninsula to save his ships from the savage storms that frequent the Athonite coast. Though it has long filled in with sediment, the path of his canal is still visible to the visitor today.

About 12,000 manuscripts, comprising one of the richest collections in the world, are preserved in the 20 monasteries of Mount Athos . Most of these manuscripts concern texts of an ecclesiastical nature, the remainder being texts of ancient Greek literature.

More than 800 manuscripts are illustrated with Old and New Testament subjects and date to the period between the 9th and 18th centuries. The oldest, such as no. 61 at Pantokrator Monastery, date back to the years shortly after the end, in 843, of the iconoclastic movement and provide invaluable evidence of the nature of Byzantine art.

Most of the illuminated manuscripts are preserved in the larger and older monasteries. Their diverse provenance and the paintings they contain, which mirror the artistic movements of the 11th, 12th and 14th centuries, are proof both of the widespread influence and of the ever-evolving nature of Byzantine art.

Illuminated manuscipts (1204-1430)

The miniatures in the manuscripts embody the aesthetic concepts prevailing in monumental painting. The only known codex of Thessalonikan provenance is that in the Bodleian Library, Oxford (Ms. Gr. th. f.1), commissioned by Demetrios Palaeologos, son of the emperor Adronikos B. This is the first "pocket book" and contains only pictures, no text. Scriptoria are known to have operated on Mount Athos in the 13th and mainly after the mid-14th century; one of them was based on the monastery of Chelanadari.

Illuminated manuscripts (867-1204)

The rich libraries of the Protaton and the twenty monasteries on Mount Athos house over 800 illuminated manuscripts. Of diverse provenance and spanning a period from the 9th to the 18th century, they provide a wonderful picture of this painting genre.

The illuminated manuscripts of the 9th to 12th centuries are few in number and most of them represent the art of Constantinople, since they originated from copyist scriptoria of that city.

http://www.culture.gr/2/21/maps/macedon/ag_oros/ag_oros.html

You are right.  Many Greeks or better East Roman citizen  had  saled  for diffrent  purposes  a lot of books as about the Byzantium (and not only ) history. A lot of them there are in the Vatican.

But except from  Agio Oros also and the Patmos island have a lot of books-sources as about the Byzantium history and the medieval times. Actually Ottomans consider the Patmos Holly island.