The Ruins of Gorlan - John Flanagan

He had always wanted to be a warrior. The Rangers, with their dark cloaks and shadowy ways, made him nervous. The villagers believe the Rangers practice magic that makes them invisible to ordinary people. And now fifteen year-old Will, always small for his age, has been chosen as a Ranger's apprentice. What he doesn't realize yet is that the Rangers are the protectors of the kingdom. Highly trained in the skills of battle and surveillance, they fight the battles before the battles reach the people. And as Will is about to learn, there is a large battle brewing. The exiled Morgarath, Lord of the Mountains of Rain and Night, is gathering his forces for an attack on the kingdom. This time, he will not be denied . . . .