How to Stop Time by Matt Haig

Tom Hazard has a dangerous secret. He may look like an ordinary 41-year-old history teacher, but he's been alive for centuries. From Elizabethan England to Jazz-Age Paris, from New York to the South Seas, Tom has seen it all. As long as he keeps changing his identity he can keep one step ahead of his past - and stay alive. The only thing he must not do is fall in love.