The Were Chronicles — Alma Alexander

Everything I knew about the Were was wrong  A Were of no fixed form, a Random, able to Turn into any warm-blooded creature it sees... A young Random whose failure to Turn forces him into taking his destiny into his own hands, becoming full Lycan in the name of pride and fury, learning things he never thought were possible... A true Shifter, the wild card, Turning into anything he chooses at will... First Jazz Marsh Turns into something unprecedented, throwing her family and the Were authorities into a spin. Then her brother Mal, frustrated beyond reason by his own delayed Turn, takes matters into his own hands and chooses his own destiny, infiltrating the shadowy Lycan clan in order to help expiate his perceived guilt in his older sister's death. He's helped by his friend, Chalky, a true Shifter who is capable of Turning into anything he pleases unconstrained by the rules of Were kind. Together, they work to turn back a shattering tragedy, solve a conspiracy-shrouded mystery rooted in their own kind, and work to preserve their own existence against a rising tide of superstition and hatred. All they wanted to do, in the end, was save a life. Instead... they started a war.