Black And White - Number 1 in series

Jet, the darling good girl of the city, uses her shadow-power to battle the forces of evil. But her shadows also mask the fierce demons that only she, her mentor, and her former best friend - and now arch-nemesis - know about. Iridium is that former best friend: able to wield the power of light, she trained as a hero only to become one of the most infamous villains in the city - for what she feels are truly heroic reasons.
Alternating between the present-day threat and their past exploits as friends, and later rivals, at the Superhero Academy, the novel brings these two women to vivid life, portraying the complexities of being a true hero in a world determined to categorise you in a neat box of good or evil - black or white.