Sacred illuminated manuscripts were produced by holy men of the Christian, Muslim, and Jewish faiths to glorify their respective deities. Christian manuscripts were produced in codex format (folded and bound), the modern form of the book. At Constantinople, Christian designs combined, then spread throughout Europe. Two distinct styles for the Great Gospel-Books emerged: Anglo-Irish in Ireland and part of England (Insular Celtic), and Carolingian (approved by the Pope). Irish calligraphers and artists often ignored new Roman viewpoints.

In The Book of Durrow, a Celtic manuscript produced about 650 A.D., motifs were derived both from Byzantine patterns and the pre-Christian Celtic Iron Age. Icons for the Evangelists differ from later Gospel-Books: Matthew - man; Mark - eagle; Luke - calf; John - lion. Letterforms are Irish-Celtic, with traditional red-dot outlines highlighting capitals. Although executed in a limited range of colors with rather primitive human portrayals, a wide variety of intricate ribbon interlacings, trumpet spirals, and geometric shapes are used in decorative borders and initials.