Yet another version of the "grail quest" forms the plot of Kate Mosse's novel Labyrinth, which has inevitably been compared with The Da Vinci Code. Those comparisons are actually fairly apt - neither book is well edited, the characters in each are quite flat, and I found that I'd guessed the "big twist" about halfway through in both cases.
This time, the story is told through parallel plotlines, one set in the present and the other set in the early years of the thirteenth century. The structure works, for the most part, and the historical aspects of the story are clearly well-researched and add much to the narrative. However, the book seems vastly over-written and spottily edited (I nearly gave up after the first couple of chapters, which are narrated in a grating, omniscent voice; thankfully that particular problem fades after a while).
As a casual read this is an adequate novel; it kept me occupied during the commutes for a few days. It's not great - don't expect Eco - but it's better than at least a few of the other Dan Brown spinoffs.