Prior to invention of the codex (precursor to the modern book), writing was typically applied to scrolls, which are also referred to as rolls. Scrolls were the dominant book form from roughly the 25th century BC to the 4th century AD.
Although movies and television shows typically having characters open scrolls vertically in order to read them, the normal practice in ancient times was to open them horizontally.
Scrolls and The Early Codex by Larry Hurtado (YouTube 11:07) – He demonstrates how scrolls were read, which was horizontally.
The codex, which followed the scroll and preceded the modern book as means of storing texts, first appeared in the 1st century AD, became the dominant book form by the 4th century, and continued as the primary format for books. Its production was transformed in the 15th century with the invention of the printing press, leading to the modern era of mass-produced books.
The codex was more portable, economical, and convenient than the scroll, as well as able to hold larger quantities of text in a single object. That said, it took an extended period of development for this volume advantage to become manifested. Here are some specifics:
- By the late 2nd or early 3rd century AD, a codex was capable of holding either all four Gospels or all the letters of Paul.
- By the mid-3rd century AD, a codex was capable of containing the entire New Testament.
- By the early 4th century AD, a codex was capable of containing the entire Old Testament.
- By the mid-4th century AD, a codex was capable of containing the entire Bible.
The Duty of a Man 