The rhythm of time
(Book)

"Seventh grader Rahim Reynolds loves testing out the gadgets invented by his brilliant friend Kasia Collins. First there were the X-ray glasses and all the trouble they caused. Now there’s the new cell phone she built for his birthday, even though his parents won’t let him have one. But Rahim is excited to use the phone to search for videos of his favorite old-school rap group. What he doesn’t know is the phone has a special battery that interfaces with a secret government satellite, which spells trouble when the phone transports him back to 1997. Almost immediately, he learns what every time traveler before him has: Actions in the past jeopardize the future. With Kasia as his only lifeline to the present, Rahim works with her to get home unscathed, all the while dodging bullies (on his end) and suspicious government agents (on hers)." --publisher's website