Cat. & Reference: Taking it on faith
Catalogers are supposed to be unbiased. We are supposed to accept, at face value, the information in the books we works we come across. If we think someone's made a mistake, we can supply corrections or explanatory notes in brackets, but that's about it.
The upshot of this is that if someone says that they channeled the spirit of a dead person who wrote a book through them, the cataloger has to put the dead person as the author. (The medium who channeled the spirit is cataloged as an "added entry," which means someone who helped out with the creation of the work, but isn't considered primarily responsible for its content. Translators, illustrators, and editors are other common "added entry" roles.)
Of course, a good cataloger also gives patrons the proper information they need to make a choice about material selection, and that information probably includes whether or not a book was written by a living person or through a medium.
The official way to distinguish between the two types of authors is to add the word "Spirit" in parentheses after the author's name. That way, the two authors show up together when browsing, but books written by each are ultimately kept separate in the catalog.
You'd be surprised at how many famous people have written books from beyond the grave. (You wouldn't be surprised, perhaps, that it's mostly famous people who seem to be doing it.)
The Library of Congress owns books written by the spirit of Sir Arthur Conan Doyle (fittingly, since he was very involved in spiritualism in his later years), as well as John Lennon, Princess Diana and Sitting Bull.
Lest I start sounding a bit smug, it's worth noting that most people (and, presumably, most librarians) don't believe that Joseph Smith actually translated The Book of Mormon from an ancient source. And yet, because he's listed as the translator on the title page of The Book of Mormon, that's how he's credited in the catalog records (such as this one).
Of course, "Mormon" isn't credited as an editor or compiler, so I guess you can only suspend disbelief for so long. And I was going to say that the records didn't include an language code variable field, either (a field that includes 3-letter codes for the language of translation and original language of the book), but then I came a cross a record which does include them (here). (The "eng" stands for English and the "und" stands for "undetermined," I guess because there isn't a standard ISO 639-2 language code for "Reformed Egyptian.")
For some reason it gives me cataloger warm fuzzies to know that some Library of Congress librarian actually bothered to add in translation codes for The Book of Mormon.