HPMOR is an excellent choice.
What's your audience like? A book club (presumed interest in books, but not significantly higher maturity or interest in rationality than baseline), a group of potential LW readers, some average teenagers?
The Martian (Andy Weir) would be a good choice for a book-club-level group- very entertaining to read and promotes useful values. Definitely not of the "awareness raising" genre, though.
If you think a greater than average amount of them would be interested in rationality, I'd consider spending some time on Ted Chiang's work- only short stories at the moment, but very well received, great to read, and brings up some very good points that I'd bet most of your audience hasn't considered.
Edit: Oh, also think about Speaker for the Dead.
Thank you for your help! I have edited my post with additional information. My audience is a general youth audience, think of promoting content to an entire high school, with "average teenagers" and people that might be more interested in content. Of course, some people will be more interested than others, so a wide variety of recommendations for different interest groups is better. I'm primarily looking for books that promote ethical/altruistic behavior, I'm not sure if any of your beforementioned recommendations do so.
Hi Less Wrong,
I've got the opportunity to promote books and other forms of content to a largely teenage audience. I'm looking for some good book recommendations and recommendations for a limited amount of other media (websites, movies, etc) that will spread awareness of positive ideas and issues in the world, while still being entertaining to the target audience. HPMOR comes to mind, and although I don't think its main focus is to promote an issue to readers, it is an excellent choice because it is well ranked, promotes rationality which can directly help readers, and is completely free to read online. Recommendations don't have to be free, but that is a very important factor.
Thanks everyone!
Edit: Thanks everyone for your contributions. I realize I was being a little too vague, I think content that promotes ethical/altruistic behavior is mainly what I am looking for, either inspiring it with fiction or causing motivation for it with nonfiction. I am looking for free web content, although paid content recommendations are also appreciated. This is for a general youth audience, not a club or any sort of interest group.