Message in a Bottle

Do the books you read have hidden messages - messages, like buried treasure revealed only to the discerning? I didn't think "Halifax" did and didn't write it with that in mind, but as I look back on the various aspects of the story, I discovered to there were a number of underlying messages of which even I, the author, was unaware.
    Before we dig in and find those precious nuggets, can you think of any novels you've read that have messages you've been able to unearth? If you can, share them with us so we can profit from your insights.