My Brother is a Superhero by David Solomons

Luke is obsessed with superheroes, but his brother is the one chosen to defend the world. A visitor from another dimension chooses to give Zack six powers to help him protect trillions of people living in both dimensions. Since Luke is the expert on superheroes, he gives Zack advice about how to behave and calls him Star Guy. They agree that Zack's identity must remain secret, but a girl in Luke's class, Lara, decides she's going to find out the true identity of Star Guy. This complicates matters, especially when she makes Luke help her, but then things get even worse. A super villain wants to stop Star Guy, a gigantic meteor is going to destroy Earth, and Zack loses his powers!

This book is a "realistic" story about a boy receiving super powers. He doesn't immediately run out to battle evil beings; he really has no idea what to do and doesn't even know his own powers. He wears a black hoodie and jeans, because tights and a cape look goofy. The plot becomes an adventure, as Luke and Lara team up and realize there are bigger problems than they imagined. The author adds humor to the story, since Zack doesn't understand his powers, he rides the city bus around town, and Lara manages to misuse many figures of speech. Solomons has succeeded in creating a light-hearted, entertaining tale about a reluctant hero.