If the author had intended to write a history book, this might have been an issue. But the story given in Tobit is an episode of family history. By all indications, the author seems to be writing about an event that really happened. He gives a family tree, and many details are quite precise regarding geography and historical chronology. But it is also possible that some passages are fictitious, with the writer’s purpose being more to teach on spiritual and moral issues, not history.