Old Man's War universe

When humanity is threatened by three adversarial races who would halt the world's expansion into space, Jared Dirac, a super-power clone, tries to discover why the scientist who gave him his DNA has revealed key military secrets.

"Humans expanded into space ... only to find a universe populated with multiple alien species bent on their destruction. Thus was the Colonial Union formed, to help protect us from a hostile universe. The Colonial Union used the Earth and its excess population for colonists and soldiers. It was a good arrangement ... for the Colonial Union. Then the Earth said: no more. Now the Colonial Union is living on borrowed time--a couple of decades at most,...