Old Man's War universe

When humanity is threatened by an alliance of 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.

A seventeen-year-old colonist stranded on a deadly pioneer world recounts how she became a pawn in a dangerous interstellar confrontation during which she was forced to use her wits and make terrible sacrifices in order to save the human race.

"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,...