Years ago I came across a book called Are Mormons Christians? The author, a Mormon himself, naturally argued that they were. Like any work of apologetics it was weak in places, and avoided the really tough questions. But I was really fascinated by the appeal that was made to the question of the canon.
The canon is the list of authoritative books Christians use, and which we usually take for granted. But how did they get to be authoritative in the first place? Muslims, as I understand it, believe that the Qur'an/Koran was delivered intact to the Prophet, inerrant in Arabic. Mormons believe their prophet, Joseph Smith, translated the Book of Mormon with a pair of magic spectacles or "seer stones". But those are not claims Jews or Christians make about their scriptures.
Leaving aside the thorny issue of the Hebrew Bible, the Septuagint and Yavneh/Jamnia, why is 2 Peter in the New Testament and not 3 Corinthians, Titus and not the Shepherd of Hermas? Who decided?
The upshot was an article I eventually put together, and still exists on my original ISP server. Someone at Trinity College at the University of Toronto decided to link to it, which is flattering, but a more recent (and hopefully better) version exists here. If I get some time later this year I want to revise it again in light of a terrific little book called The New Testament Canon.
The author, Harry Gamble (University of Virginia), is one of the leading names in the field, and he is mercifully readable for the non-specialist. In less than 100 pages the reader is treated to a thorough survey sure to raise the eyebrows of anyone who has blissfully ignored the implications of questions like those above. Definitely something to add a little curry to any evangelical's diet!