The Immortal by Angela Hunt

Claudia Fischer is a jury consultant, more affectionately known as a people reader, from New York. Claudia prides herself on her ability to read a person by observing everything about their outward appearance and demeanor. After the verdict is read on her latest case, an organization based in Rome called Global Union hires Claudia to go to Rome and help screen and hire new employees.
Asher Genzano has applied for the position of interpreter and translator. During his interview with Claudia, Asher is read as being truthful in his answers and confident in his abilities. Even so, Claudia feels there is something not quite right because his answers to her questions should make him an old man and yet he looks to be in his thirties. Despite how she feels, Claudia has no concrete evidence against hiring him, so she gives Asher her recommendation.
After he is hired, Claudia’s feelings about Asher are confirmed when he tells her that he is two thousand years old, born the same year as Jesus Christ. Try as she may, through many hours of research in a Roman library, Claudia can’t prove him wrong, but it will take an act of faith to believe him.
I really enjoyed reading this book. While I don’t feel the story is a believable one, I do feel like the author did an amazing job creating realistic characters. Angela has a gift for bringing history to life. She wrote about it in a way that made it possible for you to put yourself there.