Warstrider (Warstrider, 1)

In the twenty-sixth century, humanity is at war with the Xenophobes, and the planet Loki is the next battleground. Dev Cameron joined the military to fly a starship but is rated unsuitable and grudgingly accepts an assignment with the ground forces piloting a massive walking tank (a warstrider). But Cameron may yet get a chance at glory when he makes a discovery about their alien foes that could change the course of the war.