Ranger's Apprentice Tome 1
The Ruins of Gorlan

The Rangers, with their shadowy ways, have always made him nervous. And now fifteen-year-old Will has been chosen as a Ranger's apprentice. But what he doesn't yet realize is that the Rangers are the protectors of the kingdom. Highly trained in the skills of warfare and surveillance, they fight the battles before the battles reach the people. And now there is serious trouble 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...