The Magicians' Guild, by Trudi Canavan
The Black Magician is a very cleverly constructed trilogy. And it really pains me that I can't tell you *how* cleverly constructed it is yet. All I can tell you at this point is about the first book in the trilogy, The Magicians' Guild
The Magicians' Guild is the tale of Sonea, a girl who lives in the slums of the city of Imardin. Every year, the magicians of Imardin expel the slum-dwellers from the city, and on this year, Sonea is one of the "dwells" being thrown out. She joins a group of youths protesting the Purge. She takes a stone in her hand, gathers all of the anger in her at the injustice of the Purge, and throws the stone right through the shield protecting the magicians.
This is confusing for everyone involved. Sonea soon realizes that she is one of the magicians she has been raised to hate and fear, and the magicians learn that there is a magician in Imardin who is not one of their number. Adding to the confusion and distress, the magicians at first mistake a young man standing next to her as the one who threw the stone, and they direct too many stunstrikes at him, burning him to a crisp on the spot.
So Sonea, believing that she would be in for the same treatment if the Guild were to discover her, goes into hiding. And the Guild, not knowing if Sonea is a natural talent or a trained rogue magician, begins their search for her.
This is just such a great series, I can't begin to tell you. Imardin is a realistically drawn city with people from all walks of life -- highborn, traders and merchants, working people, and of course the underclass, of both the law-abiding and not-so-law-abiding varieties.