Twin Daggers Series by MarcyKate Connolly

Aissa's life is a web of carefully constructed lies. She and her twin sister, Zandria, are Magi spies, magic users most believe to be extinct. And they're on a mission for revenge. By day, Aissa and Zandria play the role of normal young Technocrats eager to fulfill the duties of their new apprenticeships. By night, they plot their revenge to retake their city from the Technocrats... moreAissa's life is a web of carefully constructed lies. She and her twin sister, Zandria, are Magi spies, magic users most believe to be extinct. And they're on a mission for revenge. By day, Aissa and Zandria play the role of normal young Technocrats eager to fulfill the duties of their new apprenticeships. By night, they plot their revenge to retake their city from the Technocrats. But then Aissa is given a new mission: find the heir to the Technocrat throne, who is rumored to be one of the Heartless, and kidnap her. Born without a working heart, the Heartless survive with a mechanical replacement.Aissa is more likely to be caught than to be successful, but she's never been one to turn down an assignment, even if the hunt is complicated by a kind Technocrat researcher who is determined to find a cure for the Heartless. But when Zandria is captured by the Technocrats, Aissa will do anything to get her sister back. Even if it means abandoning all other loyalties--and missions--and deciding whether or not it's worth risking everything on getting help from her sworn enemies. less

Now torn between two worlds, Aissa must decide who she can trust. Especially when it comes to her twin.Now without a home and on the run, Aissa has never felt so trapped and alone even with her sister and friend by her side. Zandria—once her other half—has become cold and inflexible after her time in the Technocrat’s dungeon and is bent on revenge Aissa no longer feels... moreNow torn between two worlds, Aissa must decide who she can trust. Especially when it comes to her twin.Now without a home and on the run, Aissa has never felt so trapped and alone even with her sister and friend by her side. Zandria—once her other half—has become cold and inflexible after her time in the Technocrat’s dungeon and is bent on revenge Aissa no longer feels. Their friend Remy may still side with his father, a Magi leader who refuses to believe his spy, Darian Azul, has turned traitor. And Aissa herself is now an enemy of her Magi people after falling in love with—and binding her heart to—Aro, a Techno prince who puts all their lives at stake.Using clues her parents and others left behind, Aissa is determined to uncover the secrets of the Alchemist Alliance that helped create her and Zandria’s unique magical powers … as well as learn whether the Alliance’s research holds the key to healing the rift between the Magi and Technocrats after centuries of war. But with her people preparing for battle, and Darian poised to use the Technocrats’ might for his own ends, it will take more than lost spells and hidden secrets to accomplish her goal. Especially as the dangerous bond between her Aro grows deeper and threatens everything Aissa has ever believed. less