Let me start with Nibley's concluding comments from the chapter I just finished reading whose notes I'm about to type up and share in the next post. In 1816, the American Bible Association decided that the apocrypha (a group of writings that claimed Biblical authority but were not in the generally accepted canon, though there's disagreement about that also since my German Catholic Bible includes several 'apocryphal' works in it too) were the work of the devil, and essentially all publication or discussion of them ceased in the US. In 1945, the last living apocrypha scholar said it was time to close the door on them and let them sink into nothingness. Then in 1946 great discoveries were made to vindicate much of the work and a new era of research into them began.
When in 1833 Joseph Smith asked God what if anything he should do with the apocrypha, God's answer was (D&C 91): "There are many things contained therein that are true, and it is mostly translated correctly; There are many things contained therein that are not true, which are interpolatinos by the hands of men. ... Whose is enlightened by the Spirit shall obtain benefit therefrom."
So finding the truth in them is left to us by the manifstation of God's Holy Spirit. One of the things I most value in Nibley's work has been to dig through the many apocryphal writings and pull out gems that unite with truths we have in the Bible, the Book of Mormon, and other modern revelation.
In this chapter, Nibley goes through a bunch of areas where the apocrypha supports the Book of Mormon. Many of them are 'oddities' about the Book of Mormon that have given skeptics pause. From the apocrypha, we learn that they really aren't oddities at all, but that Lehi, Nephi, and all the rest of them in the Book of Mormon fall into distinct, recognizable patterns of thought, speech, symbolism, and custom that were common in the ancient world but which you cannot find in the Bible and were complelety unknown in Joseph Smith's days. These are therefore intellecutal underpinnings that support a testimony of the historicity of the Book of Mormon and Joseph's prophetic call.
They also support the LDS claim that the gospel of Jesus Christ was known anciently - that Adam believed in Jesus Christ, as did Enoch, Noah, Abraham, Moses, and other prophets and faithful people from Adam's day to this. A common pattern was had in those days we term 'in the beginning,' a pattern that was spread throughout the earth in themes and variations among just about every ancient culture and civilization. (The LDS answer to Jung given years before Jung was nothing more than a Freudian slip in his father's mouth.)
These evidences are not themselves a testimony, but they support and strengthen one that already exists.
So that's the introduction. The next post has the meat.