The Unlikely Intrusion of Adams Klein (The Timefall Trilogy)

Fourteen-year-old Adams Klein lives by one simple rule: don't do anything that might change the course of history. To protect him from a murderous tyrant, Adams was hidden away in the year 2015. A refugee from the distant future, his existence is a secret. But when he witnesses a tragedy unfolding, he can't stand by and do nothing. Now history is being changed, and Adams and his new friends are being hunted by a villain who'll stop at nothing to retain his iron grip on the world of the future, even if it means destroying the past.