Outriders; a book by Jay Posey, has a disturbingly similar story to Marathon. Spoiler: the main character dies on page one. It's about super soldiers that need to die to be initiated, and have more than one body in case of death. The main character is recruited into this group, and his perspective is filled with more characters and subtleties than watered down cliches that most sci-fi books have. There are strained political relations between mars and earth because of supplies, poverty, and the militaristic nature of earth's government; (the UAF). Sounding familiar yet? These super secret "Outriders" need to stop a woman with the intention to provoke war etc. It's a great read; like a Brandon Sanderson kind of great. I just found it while sifting through my shelves today.