Labyrinth  by Kate Mosse.  Yet another bestseller about the Grail, this one actually is worth picking up if you're a fan of historical action and suspense that likes their thrillers long.  And the length is really just about the only drawback - Labyrinth clocks in at nearly 700 pages, much of which is a result of perhaps overmeticulous research.  Mosse has obviously done her homework, and wants us to know it; there's a myriad of historically accurate descriptions of clothing, language differences, and the politics surrounding the crusades and the inquisition, but I'm not convinced it was all necessary to the background of the story. 
The novel's strength is that while it's ostensibly about the Grail, there's no Dan Brown-esque extrapolation as to its nature.  What we get is a split narrative, changing between thirteenth century France, and a more or less modern archaeological dig, and the two women central to the recovery of a mysterious book.   Mosse keeps the story moving despite the length, crafting a historical thriller full of strong women that should appeal to fans of suspense novels and SCA members alike.