Byzantine art is almost entirely concerned with religious expression and, more specifically, with the impersonal translation of carefully controlled church theology into artistic terms. Byzantine forms were spread by trade and conquest to Italy and Sicily, where they persisted in modified form through the twelfth century, and became formative influences on Italian Renaissance art. By means of the expansion of the Eastern Orthodox church, Byzantine forms spread to eastern European centers, particularly Russia. Influences from Byzantine architecture, particularly in religious buildings, can be found in diverse regions from Egypt and Arabia to Russia and Romania.
In Byzantine literature, therefore, four different cultural elements are to be reckoned with: the Greek, the Christian, the Roman, and the Oriental. Byzantine literature is often classified in five groups: historians and annalists, encyclopedists (Patriarch Photios, Michael Psellos, and Michael Choniates are regarded as the greatest encyclopedists of Byzantium) and essayists, and writers of secular poetry (The only genuine heroic epic of the Byzantines is the Digenis Acritas).
The remaining two groups include the new literary species: ecclesiastical and theological literature, and popular poetry. Of the approximately two to three thousand volumes of Byzantine literature that survive, only three hundred and thirty consist of secular poetry, history, science and pseudo-science.
While the most flourishing period of the secular literature of Byzantium runs from the ninth to the twelfth century, its religious literature (sermons, liturgical books and poetry, theology, devotional treatises etc.) developed much earlier with Romanos the Melodist being its most prominent representative.