Matt Haig

"Tom Hazard has a dangerous secret. He may look like an ordinary forty-one-year-old, but owing to a rare condition, he's been alive for centuries. Tom has lived history -- performing with Shakespeare, exploring the high seas with Captain Cook, and sharing cocktails with Fitzgerald. Now, he just wants an ordinary life. So Tom moves back to London, his old home, to become a high school history teacher -- the perfect job for someone who has witnessed...

Regarding humans unfavorably upon arriving on Earth, a reluctant extraterrestrial assumes the identity of a Cambridge mathematician before realizing that there's more to the human race than he suspected.