Ender’s Game by Orson Scott Card
In order to develop a secure defense against a hostile alien race’s next attack, government agencies breed child geniuses and train them as soldiers. A brilliant young boy, Andrew “Ender” Wiggin lives with his kind but distant parents, his sadistic brother Peter, and the person…
Old Man’s War by John Scalzi
John Perry did two things on his 75th birthday. First he visited his wife’s grave. Then he joined the army. The good news is that humanity finally made it into interstellar space. The bad news is that planets fit to live on are scarce―and alien…