15 Minutes by Steve Young.
Things aren't going so well for Casey Little. He's bullied at school and is stuck being a water boy for the football team even though he wants to be out on the field. But when he discovers his grandfather's old watch in the attic, everything begins to change. Casey quickly realizes that the watch has the power to send the wearer back in time 15 minutes, and it doesn't take long before he's using the watch to his advantage. Through making countless trips back in time, he becomes a valued member of the football team, befriends the popular kids at school and even gets his revenge on a bully. However, he eventually comes to realize that there might be unintended consequences of using the watch and he's forced to decide whether it's worth using the watch if it's at someone else's expense--even someone like the school bully.
This is a quick read that is not too dense (many of the chapters are quite brief). It would make a good choice for boys in upper elementary or middle school because of its action, fast pacing and relatable male protagonist. While there are themes such as learning compassion and empathy for others, Young manages to handle them in a manner that is not overly self-conscious or heavy handed, resulting in a fun and entertaining story.