"Devil codex Gigas" by Kungl. biblioteket. Licensed under Attribution via Commons.
A codex is a book with hand-written content. Some people also use the term for books with machine printed content. Some codices are continuously folded like a concertina. Some people don't call these folded documents codices. Everywhere you go you find contrary people. What else is new?
The alternative to paged codex format (i.e. a 'book') for a long document is the continuous scroll.In the USA you are free to practice whatever religion your little heart desires, but the majority of our population comes from a Christian background, a background that goes back 2,000 years. Much of the fabric of our civilization comes from the civilizing influence of the church. There are certain precepts in our Judeo-Christian culture that are fundamental to our society and our civilization. People from a Christian background take many of these concepts for granted and assume that people from other cultures also consider these same ideas as valid and important. This is not necessarily the case and unless you take the time to understand someone from another culture, you may not discover just where your beliefs differ.
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The Romans developed the form from wooden writing tablets. The codex's gradual replacement of the scroll—the dominant book form in the ancient world—has been called the most important advance in book making before the invention of printing. The codex transformed the shape of the book itself, and offered a form that lasted for centuries. The spread of the codex is often associated with the rise of Christianity, which adopted the format for use with the Bible early on. First described by the 1st-century AD Roman poet Martial, who praised its convenient use, the codex achieved numerical parity with the scroll around AD 300, and had completely replaced it throughout the now Christianised Greco-Roman world by the 6th century. - Wikipedia (emphasis mine)