Fireborne (The Aurelian Cycle #1) by Rosaria Munda

Annie and Lee were just children when a brutal revolution changed their world, giving everyone--even the lowborn--a chance to test into the governing class of dragonriders.

Now they are both rising stars in the new regime, despite backgrounds that couldn't be more different. Annie's lowborn family was executed by dragonfire, while Lee's aristocratic family was murdered by revolutionaries. Growing up in the same orphanage forged their friendship, and seven years of training have made them rivals for the top position in the dragonriding fleet.

But everything changes when survivors from the old regime surface, bent on reclaiming the city.

With war on the horizon and his relationship with Annie changing fast, Lee must choose to kill the only family he has left or to betray everything he's come to believe in. And Annie must decide whether to protect the boy she loves . . . or step up to be the champion her city needs.