Let me save you the trouble here...skip this trilogy! The first book was okay and it went downhill from there.
Summary from goodreads.com:
After leaving Society to desperately seek The Rising, and each other, Cassia and Ky have found what they were looking for, but at the cost of losing each other yet again. Cassia is assigned undercover in Central city, Ky outside the borders, an airship pilot with Indie. Xander is a medic, with a secret. All too soon, everything shifts again.