Suppose you're looking at a table with two copies of the Latter Day Saint book of scripture known as The Book of Mormon sitting on it. Do you refer to the two books as Books of Mormon or Book of Mormons? Or is there some other way of succinctly referring to the plurality of the items resting on the table?
According to my boss the grammatically correct reference is Book of Mormons because, as she puts it, the book is only one book, no matter how many copies of it there are, and it's the title that's being pluralized, not the Mormons.
I generally try to say Books of Mormon because the other term makes it sound like a book that the Mormons use. That, or that it was compiled by more than one person named Mormon. But, is my way the proper way? If so, then the plural of terms like power of attorney becomes powers of attorney which would imply more than one power, thus rendering the phrase technically inaccurate. I think.
What a conundrum. Maybe the answer lies in the very first sentence of this post. It just might be best to refer to them as copies of the Book of Mormon. Except that doesn't solve the powers of attorney problem. Then again, maybe I've incorrectly identified it as a problem.