Theologically, the unity of Scripture marks out clear limits of thought and behaviour beyond which individuals or ‘churches’ may not legitimately be called Christian. On the other hand, the diversity of Scripture demonstrates how no one sect or ecclesiastical tradition has a monopoly of the truth. One can become heretical by being either too broad-minded or too narrow-minded!
[C.L. Blomberg, “The Unity and Diversity of Scripture” in New Dictionary of Biblical Theology, 72]
This article lays out the unity and diversity found in the Old and New Testaments. It is extremely helpful in thinking through how the Bible is one book and not 66 books put together by some council. Instead, there exists a canon that is evidenced in the storyline of the Bible. I think the quote above could help us in our desire to see unity in the Body of Christ, realizing that there will also be diversity.