Magdalene tells the story of, of course, Mary Magdalene as she tells her story to a Roman magistrate before she is executed. She tells of how she was a saleswoman and of how she came to be inhabited by evil spirits, and of how she met Jesus. It all started when her house was raided by Romans, who killed her husband and baby in the attack. That incident drove her into depression and eventually to following Satan.
The book also parallels with the story of a centurion who attacked Mary's house and his search for the truth. Because he has a secret, a secret that only a tag-along prostitute knows.
The book is well written and I feel that the historical details were correct. Hunt came up with an interesting reason of why Mary was inhabited by so many spirits at once. The story is believable, and since it's historical, there's not much else to say about it.