The Koran defines Muslims, along with Jews, Sabians, and Christians, as “people of the book.” This makes sense in a Islamic context, because the Koran is the Word of God made text. Moreover, by the time the Koran was spoken (and later written down), both Jews and Christians had a defined canon considered to be inspired, and a process to preserve the inspired text relatively uncorrupted from additions and errors.
Most modern Christians would agree with the Islamic assessment of themselves as being people of the book. After all, they have the bible, which they refer to as Sacred Scripture and as the Word of God. And yet it is unlikely that the ancient Jews, or the earliest Christians, would have defined themselves as people of the book, for they had no such book.
Judaism was in flux during the time of Christ, with multiple canons and textual traditions; the canon of the Hebrew Scriptures was not formalized until the 3rd century, and the differing textual traditions were not merged into a single text until the 9th century Masoretic text. Meanwhile primitive Christianity used the Septuagint text as Sacred Scripture, but the various New Testament writings only gradually became thought of as scripture, and the current canon of the New Testament was not formalized until the 9th century.
In the ancient world, the oral word was primary; the written word was of little importance, useful only to a very small class of people in government, religion, or business. John H. Walton and D. Brent Sandy write:
After the discovery of writing, whether for the Egyptians or Sumerians, the Greeks or Romans, it was often only the priestly or commercial elites that acquired enough literacy to carry out their duties (or they purchased slaves who had been trained to read and write on behalf of their masters). Beyond that, the wealthy may have been educated enough to be literate. For the general populace literacy was rare, for it was almost never a necessity. (Walton and Sandy 2013, 90)
This seems odd to us, being raised in a literate culture, one in which someone who is illiterate is seen as uneducated, backwards, and unintelligent. And yet, even in our literate age, people learn to speak before they learn to write; and the mass media of television and radio are oral means of communication. Speaking and hearing are fundamental; reading and writing come later. Walton and Sandy write:
Fundamentally, speaking is primary; writing is derivative. So it is in the Bible: nothing in the biblical creation accounts suggests that God wrote or created writing. Speaking was the focus; writing would come later. So it is for children: learning to speak is essential and comes first; learning to write is helpful and comes second. So it has been in history: a society that does not speak to one another has never existed ; a society that does not write to one another has always existed. (Walton and Sandy 2013, 89-90)
This may be hard for us to grasp, but the bible was primarily oral before it became the written text we know today. In the synagogues, the reader would translate the written text on the fly into the vernacular tongue. In the early churches, Christians would gather together to hear the Gospels and the epistles read to them. Even today, we gather together to hear the scriptures read to us, after which we hear a sermon or a homily, usually interpreting the text we just heard. The distinction between an oral culture and a textual culture revolves around the question of authority. Walton and Sandy write: “For oral communication, authority focuses on the persons who transmit the tradition. In written communication, authority shifts to the words on the page.” (Walton and Sandy 2013, 89)
In an oral culture, the speaker is the one who transmits the tradition. In other words, it is the speaker who determines what is said, and how it is understood. In a textual culture, the hearer is responsible for determining what the author meant, irrespective of the tradition. And thus it is that modern Protestantism, which developed side by side with the Gutenberg press, is compelled to disregard the oral tradition in favor of its own interpretation. And having disregarded the apostolic tradition (2Th 3:6), it is no wonder that each reader, having determined a new meaning in the text, is compelled to create a new denomination, leading directly to the confusion of denominations.
If, as the scriptures state, “God is not the author of confusion” (1 Co 14:33), is it possible that we are approaching Sacred Scripture incorrectly? That the God who spake the worlds into existence, who commanded the prophets to speak the words of God unto the people, and who gave prophets, evangelists, and teachers unto the church, expects the oral transmission of tradition — including Sacred Scripture?
Walton, John H, and D. Brent Sandy. The Lost World of Scripture: Ancient Literary Culture and Biblical Authority. Downers Grove: InterVarsity Press, 2013.
 The Sabians seems to refer to a variety of monotheistic faiths that are neither Jewish nor Christian, although they appear to have more in common with Christianity than with Islam.