John Byron has the postmortem here.
I am not sure where to begin with this book. I can’t provide a serious review because it is hard for me to believe that he published it with a straight face. This book is horrible on so many levels. O’Reilly claims that he and his co-writer, Martin Dugard, have uncovered a narrative about Jesus that is fascinating and frustrating; a story that has not been fully told until now in this book (pp. 2, 4). However, a simple read of any undergrad Introduction to the Gospels textbook would demonstrate that O’Reilly doesn't know what he is talking about.
Of all the problems with this book it is his complete lack of understanding about history that is most frustrating. He claims to separate myth from history, but I don’t think he knows the difference. He certainly doesn't have a coherent methodology. Not only does he not understand how history writing works (both now and in antiquity), it is obvious that he makes it up as he goes along or he just gets it plain wrong.