As for the Book of Mormon... try to think of it this way.

Imagine that, tomorrow, you meet aliens from a faraway star system. The aliens look like giant jellyfish, and are in fact aquatic; needless to say, they grew up in a culture radically different from ours. While this alien species does possess science and technology (or else they wouldn't make it all the way to Earth !), they have no concept of "religion". They do, however, have a concept of fiction (as well as non-fiction, of course, or else they wouldn't have developed science).

The aliens have studied our radio transmissions, translated our language, and downloaded a copy of the entire Web; this was easy for them since their computers are much more powerful than ours. So, the aliens have access to all of our literature, movies, and other media; but they have a tough time making sense of some of it. For example, they are pretty sure that the Oracle SQL Manual is non-fiction (they pirated a copy of Oracle, and it worked). They are also pretty sure that Little Red Riding Hood is fiction (they checked, and they're pretty sure that wolves can't talk). But what about a film like Lawrence of Arabia ? Is that fiction ? The aliens aren't sure.

One of the aliens comes to you, waving a copy of The Book of Mormon (or whichever scripture you believe in) in its tentacles (but in a friendly kind of way). It asks you to clarify: is this book fiction, or non-fiction ? If it contains both fictional and non-fictional passages, which are which ? Right now, the alien is leaning toward "fiction" (it checked, and snakes can't talk), but, with us humans, one can never be sure.

What do you tell the alien ?