Jeremy and the Enchanted Theater by Becky Citra

This little book is mixes Greek mythology with modern theater to tell the story of a boy who learns how to be brave.
Jeremy’s on his way home from school and he’s scared! He hates going past the house of a mean boy and a house where a mean dog lives. He’s scared of them both, and he wishes he were brave. The mean boy throws a rock at a cat, while Jeremy hides. Little does he know that the cat will be his guide on an amazing adventure!
Jeremy discovers that he’s lost, so he follows the cat into a building labeled The Enchanted Theater. And before he knows it, he and the cat, whose name is Aristotle, have time-traveled back to ancient Greece, where he tries to solve a mystery about the theater. In the process, he has several terrifying experiences, including confrontations with the gods Zeus and Ares, that teach him that he’s braver than he thought.