Old Man's War by John Scalzi

Humanity finally makes it to space and finds out it’s quite crowded with everyone jockeying for colonies. The story goes through the experiences of your average earthling as these revelations are discovered in old age as he signs up for the military.

Notable Quotes:

“The universe is a big place. Maybe we're not in the best neighborhood.”
― John Scalzi, Old Man's War

“Now, you may think that this is some sort of generalized hatred that I will carry for the lot of you. Let me assure you that this is not the case. Each of you will fail, but you will fail in your own unique way, and therefore I will dislike each of you on an individual basis.”
― John Scalzi, Old Man's War

“When you're a teenager and you're in love, it's obvious to everyone but you and the person you're in love with.”
― John Scalzi, Old Man's War

“You do what you have to do to give people closure; it makes them feel better and it doesn’t cost you much to do it. I’d rather apologize for something I didn’t really care about, and leave someone on Earth wishing me well, than to be stubborn and have that someone hoping that some alien would slurp out my brains. Call it karmic insurance.”
― John Scalzi, Old Man's War

“What is it like when you lose someone you love?” Jane asked. “You die, too,” I said. “And you wait around for your body to catch up.”
― John Scalzi, Old Man's War