Most good stories start with a fundamental list of ingredients: the initial situation, conflict, complication, climax, suspense, denouement, and conclusion. Great writers sometimes shake up the recipe and add some spice.
Exposition
The Rose Ceremony… Er, Match Banquet
Cassia's futuristic society is matching its sixteen-year-olds with their ideal mates, and Cassia gets paired up with her best friend Xander—yay. This Match sets the stage for all the events that unfold.
Rising Action
A Rare Malfunction
Not so fast… A glitch shows Cassia a second match—mysterious Ky—and as soon as the possibility is introduced, she starts falling for him. Obviously this complicates things, since we know their relationship can't last and that chances are more than decent they'll get caught.
Climax
And the Other Shoe Drops
Cassia and Ky get caught (duh), and she's forced to make a decision about his future. You know that saying about letting the person you love go? That's exactly what Cassia does, putting Ky's happiness above her own and sending him on to what she thinks is a life of more opportunity. This is the moment we've been dreading all along, and Cassia's decision has ramifications for everyone.
Falling Action
Things Aren't What They Seem
Turns out Cassia isn't sending Ky off to a better life—she's sending him off to fight a war. Instead of a brighter future then, she's really sent him to his death. Oops. The fact that things don't turn out as expected tells us that unlike a standalone book, Cassia's and Ky's stories aren't quite over.
Resolution
Setting Up Book 2
Cassia makes the choice to find Ky, aided by her parents and Xander (what a good friend). Resolution, shmesolution—this book is the first in a trilogy, so instead of a tidy ending, our interest is piqued for the next installment in this saga.