There are lots of ways we learn through the written word. Textbooks are the most obvious, though not always very effective in and of themselves. Nonfiction books can be a great way to learn about almost anything you can imagine--cultures, history, technology, or just the lives of interesting people.
We can learn through novels as well. Hard-working authors who do their research can infuse factual tidbits seamlessly into the plot, and we can learn through a character's choices and their evolution through the story.
It recently occurred to me that there's a key difference between the nonfiction and fiction approaches to learning, though. Nonfiction generally sets out to teach--that's the whole point, to be informative. In fiction done right--in my opinion--it's up to the reader to learn, and what they take from the story can vary. The parallels they draw will depend on their own worldview and experiences, and that's what makes it so fun--that feeling of finding your own meaning.
What happens, however, when someone sets out to write a novel with the nonfiction writer's intention of teaching in mind? Does it still work? I'm not sure. I haven't tried it myself. Do you get a "moral of the story" or after-school special feel as a result? If so, that could be a problem. I can't speak for all teenagers, but my students are master cynics. If they sense a story's been contrived to teach them something, brace for imminent eye-rolling.
Does it come down to ensuring Story trumps Message? Is it more a matter of not talking down to your audience? Or are those two related? Something to think about as I dig through the latest YA works to find books to recommend to those charming cynics.