Halo: Parasite's Wake - Tim Lebbon

An original novel set in the Halo universe--based on the New York Times bestselling video game series! n2552. As the planet Reach falls to the alien alliance known as the Covenant, a lone human ship--the UNSC Pillar of Autumn--fled into slipspace and has arrived at a place that could change the course of this decades-long war.

An ancient, mysterious ringworld: Halo. n n With human forces scattered across the surface of this immense alien construct, Staff Sergeant Marvin Mobuto must now lead his fellow crewmates--survivors from the ship's brig--back to the Autumn's crash site to rally and regroup with their allies. Desertion, drunk and disorderly, and murder are only a few of the charges that Mobuto's squad carries--and keeping them in line might prove to be just as difficult as surviving the zealous, entrenched Covenant warriors who believe they have found the gateway to paradise.

n n But as war rages across the ring's landscape for control of the installation's weapons and secrets, a far more terrible threat from deep within Halo's underworld is hellishly unleashed that transforms this conflict into a desperate battle of survival for UNSC and Covenant alike...n