The Tomorrow Paradox — Keith B. Darrell

Mackenzie Mortimer was a typical junior high geek: shy, awkward, and always late for class. There was never enough time to do everything he needed to do; after all, there are only 24 hours in a day. But when Mac found his grandfather's pocket watch buried deep inside a trunk, he discovered his days have an extra hour. According to his grandfather's journal, the eccentric inventor's pocket watch can add up to 60 minutes to a single day by freezing time around whomever holds the watch and presses its button.

But when Mac confronted the mysterious time traveler who had been stalking him, his pocket watch was destroyed. Now Mackenzie Mortimer's troubles are just beginning! Mac finds himself a stranger in a strange land, surrounded by familiar people he doesn't really know, with only Gemma, a 15-year-old clone, to guide him through the labyrinth of the future. Will the mysterious black, iron key unlock the secrets to returning him home, or is it a harbinger of his impending doom?