Questioning author-ity

I was thinking about this today:

In the beginning of a story, the author shows the reader a character.  The reader takes the details supplied by the author to build a mental version of the character in her own head.  At this stage, whatever the reader knows about the character is determined by what the author chooses to provide.  If the author says the main character loves lobster and suffers from insomnia and fights with his father, then by golly, that's the way it is.

However, there comes a poin