STAR QUEST by Patricia Lee Macomber: Cara Bishop already saved the world. Now, with the war over and the aliens defeated, she's teaching other pilots to fly the alien ships that turned the tide...until the government approaches her about joining a super-secret mission, that is. Steve Hunter is the product of alien DNA. He was created in a lab, designed to destroy the aliens in a ground war that was never fought. Now, they're finally putting him to use as the leader of this new mission.
VENGEANCE by A.J. Scudiere