Young adult science fiction is some of the most action packed fiction that exists. Almost every single on this list is a wild ride through a new and interesting world, whether that be the dystopian future of our world, as in the ever-popular Hunger Games, it's distant past seen in Westerfeld's alternate history epic Leviathan, or distant planets like the landscape of Frank Herbert's Dune. That's not to say that these books are simply glossy, popcorn action books. Many of these novels tackle some surprisingly deep issues.
Suzanne Young's The Program is an emotionally gripping tale about the power of memory and the ethics of manipulating those memories.
The Giver deals with the price that a utopian society costs; House of the Scorpion talks about the ethics of cloning.
In addition to the normal trials of just being a teen, YA sci-fi protagonists also face incredible odds, whether it's surviving an alien invasion like Cassie in The 5th Wave or fighting against a corrupt government, as seen in Unwind, or even just trying to remember who they are like Jenna in The Adoration of Jenna Fox.
There's something for everyone in this list whether you're new to the genre or a seasoned veteran.
If you're a fan of romance, check out All Our Yesterdays, a dystopian time-travel romance. If you like robots, make sure that you read Cinder, a retelling of the classic fairytale Cinderella with cyborgs and aliens. If space travel is your thing, try Heinlein's time-honored, Have Space Suit, Will Travel. If you love video games: Video game fanatics will flock to titles like Ready Player One and Little Brother. If you're a fan of epic, space opera sci-fi, Dune is right up your alley, and if you're new to the genre, Ready Player One and Zoe's Tale offer a great jumping off point.
In any case, get ready for a great ride because these books are worlds of fun!