The book is FICTION .... There are some facts in there, most of the story is fiction.
"historical facts" ... I'd say no, since the winners write history
I read several other books about Jesus and that he might have had a son, there is simply A LOT of controversial stuff on both sides. Maybe believing a little bit from both sides might be a good approach?!
Will we ever know the whole truth ... probably not!
Cheers!