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I read half a book in a library a while ago that followed a guy from the first set of marines to actually go fight. They have gel-pod-beds to survive accelerations in space. after the first mission, which goes poorly, he gets back to earth like 20 years later and finds everyone else got really old, there's massive crowding, and society has gotten very corrupt. He rescues his fellow female marine from her family farm, and they go back into service, wanting to escape but not really being able to deal with society as it races past them.
Any ideas on what this book is called?