@epicaddie2, that’s an interesting question. I’d argue that any book has a message, whether the author necessarily intended it or not, but it’s not always a good or true one–and I assume that’s what you’re looking for. One book I thoroughly enjoyed as a child was The House of Sixty Fathers by Meindart DeJong. It’s more of a Middle Grade reading level, I suppose, but still really good. For teens, have you read any of Madeline L’Engle’s Sci Fi series? Or the Prydain Chronicles by Lloyd Alexander? A fine new read for me just recently was The Curse of Kalathan, by the new-to-me (and I think new) author, Kate le Roux.
I loved The Eagle of the Ninth, @sparrowhawke! Actually, the whole series is great (as are most of Rosemary Sutcliff’s books,) but if I had to choose a favorite, that might be it.