Starship Troopers by Robert A. Heinlein
It is told through the eyes of Starship Trooper Johnny Rico, from his idealistic enlistment in the infantry of the future, through his rigorous training to the command of his own platoon of infantrymen. His destiny is a galactic war of unlimited violence and destruction, in which he and his fellow troopers scour the metal-strewn emptiness of space to hunt down a terrifying enemy - an insect life form which threatens the very future of mankind.