Fractured: Dereck Dillinger and the Shortcut to Oz by Eddie McPherson

Dereck, is a normal thirteen-year-old boy who has agreed to take care of his five-year-old sister, Jessie, while their mother is away overnight. As the big brother, he intends to keep his sister safe, taking on the role of their dad who died in a car accident the year before. Jessie only wants to be read fairy tales, and she begs Dereck to read her the stories, though he would prefer they do anything else. When a violent storm moves in, Dereck stumbles into the cellar of their home, while Jessie is trapped upstairs, screaming for him. Trying to get to her, he falls through the cellar floor and wakes up in Oz - an Oz filled with all the fairy-tale characters Jessie loves so much. Now Dereck must battle dangerous and tricky creatures as he attempts to take a little-known shortcut to a Wizard who Dereck hopes can send him back upstairs where his sister is alone and screaming in the eye of a raging storm.