Ever noticed that some Mormons (the biblical literalists, especially) will insist that Moses wrote Genesis, as per the ancient tradition? Then those same Mormons will insist that Joseph Smith did not write the Book of Mormon?
Why the double standard? How come writing a religious “history” of an ancient people from whom he claimed descent makes Moses a prophet but makes Joseph a fraud?
Say that you tell these Mormons that Genesis, as we have it, was not authored by Moses but is the product of several scribal traditions writing in different eras with different agendas centuries apart from Moses’ lifetime. For them, such a proposition delegitimizes Genesis, takes away from its being “true.”
Now, tell those same Mormons that the Book of Mormon, as we have it, was not authored by Joseph Smith but is the product of several scribal traditions writing in different eras with different agendas centuries apart from Joseph. This would affirm the truthfulness of the Book of Mormon for them!
The situation is wonky with the critics of scripture, even! To weaken Genesis’ cultural authority they strive to distance it from Moses, even questioning his existence. For whatever reason that strategy is reversed for the Book of Mormon, whose critics strive to diminish its cultural authority by strengthening its connection to Joseph Smith, very much insisting that he really was behind it!
So, here are my thoughts. I am neither attacking the Book of Mormon nor Joseph Smith’s prophethood. No, on the contrary, I don’t think either is taken seriously enough. I cannot understand why some Mormons think Joseph recovering a history is a greater display of seership than if he had dictated a text from pure inspiration. Think on that, a text, a divine narrative, straight from heaven!
I do not reject the testimonies of the eleven witnesses or Joseph’s encounters with Moroni; I trust and accept the historicity of it all. Remember though, while we’re talking about witnesses, that everyone who observed the “translation” process (of the Book of Mormon) recounted that the plates sat on a table, inert and under cover, apart from Joseph and his scribes.
To be honest, I believe the Book of Mormon (as we have it) is a divine expansion of an ancient text (please see my essay, The Nature of Inspiration, for more of an explanation). The Book of Mormon has components both ancient (like all the chiasmus and Nahum and the like) and modern (like its Americanisms, anachronisms, and the KING’S ENGLISH).
If you ask me, the Book of Mormon as a product of Joseph’s divine inspiration makes him a greater prophet than it ever could if considered a mere transmitted history. If Moses, whose existence is challenged, is thought a great prophet for having written Genesis, how great a prophet then is Joseph (as a seer, not a man) who definitely lived, who definitely produced genuine scripture? Come on Mormons, Joseph’s critics already insist it was him, when will we let them know that that makes it all even truer than before?
 For an excellent explanation of the authorship of the Old Testament from a Latter-day Saint perspective see David Bokovoy’s “Authoring the Old Testament: Genesis–Deuteronomy”