The Books of Magic vol 5 - Girl in the Box

Possessing infinite magical powers, Tim Hunter will become the Earth's greatest sorcerer. But as the fourteen-year-old boy begins his ascension to powerful mage, he must navigate the everyday travails of adolescence. Looking to escape his personal troubles, Tim runs away to America only to find his problems multiplying. Allying himself with a shape-shifting succubus in the form of a female model, the young wizard learns lessons of treachery and friendship as he contends with a seductive mermaid who is lost in the desert and Cupid and Psyche, two disillusioned gods looking to adapt.