In my research before starting to write the speculative thriller, THE GRAIL CONSPIRACIES, I read and reread Peter Partner's THE MURDERED MAGICIANS: The Templars and their Myth.
As a matter of fact, I ended up buying the same book twice, and passed it on to one of my undercover sources for all sorts of interesting and weird stuff, whose name is Larry Crum.
From the website for my speculative political thriller, THE GRAIL CONSPIRACIES