Halo: Last Light Protocol

Reach is gone, and the Covenant has already found its next target. You are a Spartan-II aboard the crippled UNSC Enduring Wake, defending six million colonists from an invasion fleet you cannot defeat head-on. Your best weapon is Lyra, the ship’s brilliant Smart AI, but she is days from her mandatory seven-year termination. The colony can still be saved. The enemy carrier can still be destroyed. Lyra may even survive. You probably cannot have all three.