Eldest by Christopher Paolini #2

Darkness falls… despair abounds… evil reigns… Eragon and his dragon, Saphira, have just saved the rebel state from destruction by the mighty forces of King Galbatorix. Now Eragon must travel to Ellésmera, land of the elves, for further training in the skills of the Dragon Rider: magic and swordsmanship. But chaos and betrayal plague him at every turn, and nothing is what it seems. Before long, Eragon doesn’t know whom he can trust.
Will the king’s dark hand strangle all resistance? Eragon may not escape with even his life. . . .