Spellslinger by Sebastian de Castell

MAGIC IS A CON GAME . . . 

Kellen is moments away from facing his first mage’s duel and the start of four trials that will make him a spellcaster. There’s just one problem: his magic is gone.

As his sixteenth birthday approaches, Kellen falls back on his cunning in a bid to avoid total disgrace. But when a daring stranger arrives in town, she challenges Kellen to take a different path.

Ferius Parfax is one of the mysterious Argosi – a traveller who lives by her wits and the three decks of cards she carries. She’s difficult and unpredictable, but she may be Kellen’s only hope