Blood of the Chosen (Burningblade & Silvereye)

"Gyre finally sees a way to overthrow the all-powerful Twilight Order. But he'll have to gain the alliance of both the ghouls and the human rebels to the south in order to even stand half a chance. And uniting them won't be so simple. His sister Maya is still a soldier of the Order. But after clashing with her brother, she isn't so certain where her loyalties lie. Chasing the origins of a mysterious artifact to a long-lost library, she just might find the answers she's looking for"--