I've got a good grounding on the crusades, and a better one on the monastic knightly orders involved. However when I read this book,I felt nothing but disgust by the way they were portrayed. My take on this book is that it is nothing but an excerise in bashing anything christian, from The Templars, The Hospitalliers and even the Cathars. It was just one insult after another that made my blood boil, I only read it to see if the plot turned out the way I was expecting, it did.
Well written, but historically flawed and hugely biassed, don't read if you like facts.