The Dragon of Trelian by Michelle Knudsen
Calen a mage's apprentice is not especially good at doing magic. Princess Meglynne wasn't particularly good at being prim and proper. She certainly never imagined that she would tell her biggest secret to anyone let alone a common street urchin. Calen could never imagine that he and Princess Meglynne would become friends and that she would need his help.
Lately Princess Meglynne thinks that she can feel the dragon's thoughts in her mind, calling to her, even though he is far away. Calen is the only one who can help her sort out what is happening with the dragon that she has raised from a baby. Calen begins to search his master's library to find a solution to the problem they are facing.
Together they discover that their unlikely friendship is the only thing that will save the kingdom of Trelian from tragedy. Can a princess, an apprentice, and a dragon combine strength and magic to bring down a secret traitor before it is too late?