Halo: The Thursday War — Karen Traviss

Welcome to humanity's new war: silent, high stakes, and unseen. This is a life-or-death mission for ONI's black-ops team, Kilo-Five, which is tasked with preventing the ruthless Elites, once the military leaders of the Covenant, from regrouping and threatening humankind again. What began as a routine dirty-tricks operation―keeping the Elites busy with their own insurrection―turns into a desperate bid to extract one member of Kilo-Five from the seething heart of an alien civil war. But troubles never come singly for Kilo-Five. Colonial terrorism is once again surfacing on one of the worlds that survived the war against the Covenant, and the man behind it is much more than just a name to Spartan-010. Meanwhile, the treasure trove of Forerunner technology recovered from the shield world of Onyx is being put to work while a kidnapped Elite plots vengeance on the humans he fears will bring his people to the brink of destruction.