To me, the essence of any good young adult story is two-fold. First, there is the element of an innocence that is being broken open and exposed, a young person sidling up to adulthood without all the trappings of wisdom, experience and baggage that we adults have. And second, there is an aspect of rebellion, of throwing off what we've been taught, or told, or been held to as children. Our parents, or guardians, or society say "No" and we say "Hell yes!" and we go for it.
Both of the stories I chose had these elements in spades. They also had a strong voice, a compelling plot, and a satisfying ending, always things I look for.
And finally, both stories involve young adults grappling with a call to the arts, something I can certainly relate to as a writer. Oh, how I wish I'd listened to that call when I was a young adult, instead of waiting until the ripe old age I am now. But, it is never too late to embrace our inner young adult, and so I give you "One Sixth Gravity of the Heart" and "To Sail the Winds of Song." May your heart, whatever age it is, be renewed by reading them.