In my post about Attack of the Clones below I mention the Knights Templar. Here are some books regarding those ill-fated Knights:
:: The Templars: The Dramatic History of the Knights Templar, the Most Powerful Military Order of the Crusades, by Piers Paul Read. This book has been firmly ensconced on my "To Read" pile for a long time now. I really should get to it....
:: Dungeon, Fire and Sword: The Knights Templar in the Crusades, by John J. Robinson. This is one of my favorite history books. Robinson writes with a grand sweep of history, and he was a fine historical storyteller, able to make the actual events of history as rivetting as any of the sensational speculations that have gathered around the legendary Templars.
:: Born In Blood: The Lost Secrets of Freemasonry, by John J. Robinson. This book describes how some of the Templars escaped their ruthless purge and settled in Scotland, helping the Scots to break free of their Plantagenet rule and eventually form the basis for what became Freemasonry. A fascinating book.
:: The Temple and the Lodge, by Michael Baigent and Richard Leigh. This book also deals with the Templars in Scotland and their role in the beginnings of Freemasonry.
The books named above are historical works, concerned with the actual history of the Knights Templar. The legends surrounding the Templars have grown through the years, and the Templars figure into a number of historically-based conspiracy theories. A few books in this vein are:
:: Holy Blood, Holy Grail by Michael Baigent, Richard Leigh, and Henry Lincoln. Now this is what all good conspiracy theories should be: large-scale, ambitious, and a little bit blasphemous. Here the Templars become stewards of a long-lost bloodline sired by Jesus.
:: The Templar Revelation: Secret Guardians of the True Identity of Christ, by Lynn Picknett and Clive Prince. Another fine gonzo theory involving the Templars and Christ -- but not necessarily Jesus. Yes, you read that right.
:: The Lost Treasure of the Knights Templar: Solving the Oak Island Mystery, by Steven Sora. Legend has it that when the Templars were purged, their vast hordes of treasure were placed aboard several ships which sailed and then were never seen again. And then, 200 years ago, an ancient vault was discovered on Oak Island, Nova Scotia....
And finally, a good novel involving the Templars:
:: Foucault's Pendulum, by Umberto Eco. Not the easiest read, but this book involves a group of conspiracy researchers and the theories they create from all manner of medieval esoterica.