While older books can be good, I would give more thought to pursuing books outside of the Western Canons, there are a lot of points of view and perspectives to be heard that are often ignored by it. As young teens, they are at a perfect age for a lot of good books from far broader range of views. Adichie gave a wonderful speech on the issues of the single story of Western cannon (and her books are quite good as well).
Here are some that fit around what you've said is liked:
Darkest Powers and Darkness Rising Trilogies by Kelley Armstrong, great YA. Quite dystopian, more fantasy than sci-fi though both come into play. If enjoyed, the author has a wealth of books that fit into the categories you've mentioned (the trilogies fit into the Women of the Otherworld series, which is 13 novels plus additional novellas, they include the same types of things but the adult stories tend to go into more details about things of an adult nature so it would depend on your teens sensitivity).
The Night Wanderer by Drew Hayden Taylor (Native Gothic).
Where the Mountains Meets the Moon by Grace Lin (Fantasy meets Folklore meets Journey story)
Ninth Ward by Jewell Parker Rhones (Ghosts story involving Hurricane Katrina, so quite dystopian)
The Bella Balistica series by Adam Guillain - high action adventure
Almost anything by Malorie Blackman (current Children's Laureate) particularly her Noughts and Crosses series and Cloud Busting.
The Mighty Miss Malone by Christopher Paul Curtis (b
Anita and Me bu Meera Syal (Story set in 1970s England)
Nevada by Imogen Binnie (Dark comedy)
The absolutely true diary of a Part-time Indian by Sherman Alexie