In the early Middle Ages, the production of copies of the Bible in its entirety was rare, if only because of the huge expense of the parchment required. Individual books or collections of books were produced for specific purposes. From the 4th century Gospel Books were produced for liturgical use, as well as private study and as "display books" for ceremonial and ornamental purposes. The Codex Washingtonianus (Freer gospels) is an early example of a book containing only the four gospels, in Greek, written in the 4th or 5th century. By the 7th century particular gospel texts were allocated to days in the liturgical calendar; previously gospel readings had often worked through the books in sequence. Many of these volumes were elaborate; the Gospel Book was the most common form of heavily illuminated manuscript until about the 11th century, when the Romanesque Bible and Psalter largely superseded it in the West. In the East they remained a significant subject for illumination until the arrival of printing. The Evangelist portrait was a particular feature of their decoration. Most of the masterpieces of both Insular and Ottonian illumination are Gospel Books, and there are very many Byzantine and Carolingian examples.
But most Gospel Books were never illuminated at all, or only with decorated initials and other touches. They often contained, in addition to the text of the Gospels themselves, supporting texts including Canon Tables, summaries, glossaries, and other explanatory material. Latin books often include the Letter of Jerome to Pope Damasus where Jerome set out to the Pope the reasoning behind his new Vulgate translation and arrangement of the texts, and many Greek ones the Epistula ad Carpianum (Letter to Carpian) of Eusebius of Caesarea explaining the Eusebian Canons he had devised.
Luxury illuminated gospel books were mainly a feature of the Early Middle Ages, as the evangeliary or a general lectionary gradually became more common for liturgical use, and other texts became most favoured for elaborate decoration.