The New Testament consists of four accounts of the life of Jesus, an account of what his disciples did after Jesus left the scene, some essays on the meaning of the Christian beliefs, several letters to various persons and churches offering advice and guidance, and one book of prophecy.
At what point in history were these writings sanctified as divinely inspired, equal to the Torah and the Septuagint in authority? I presume that every word ever committed to paper by the Apostles didn’t end up preserved. Although the Apostles obviously were enormously respected, who decided that these writings were not merely instructional like, say, the writings of C.S. Lewis, but the actual Word of God?
Here is a good website on the development of the New Testament Canon. It was certainly not without controversy. Constantine was the one who finally called a big council together to vote on what the canon should be. Since he was emperor, this decision was pretty much final, at least within Rome. Many Christian churches outside of Rome used different canons for centuries later. The Ethiopian church used the Diatesselon (sp?) and the book of Enoch right up through the 18th century, IIRC.