I found this book to be an average read only. There are far worse books in this genre than this one, as there are far better. The book was typical of the religious thriller/dark secret genre - including a sexy and smart female protagonist (Dr. Charlotte Hennessey), the evil Vatican Secretary of State in Cardinal Santelli, an assassin named Salvatore Conte, and a hidden tomb/scrolls that would destroy Christianity if revealed.
I won't go into too much detail with the plot as previous reviewers have written on it already and the book's synopsis does the job adequately. In fact, you could read the synopsis and not need to read the book at all - it does exactly what it says on the tin. There are largely no surprises, and very few twists and turns. Suffice to say the plot is set in two locations - 1) the Vatican where Hennessey and her colleague Dr. Bersei investigate the contents of an ossuary containing, surprise surprise, a crucified man 2) Jersualem where the Jewish and Muslim authorities try to restore order following a theft from the Temple Mount. Here, a British arachaeologist, Graham Barton, also discovers an ossuary (along with eight others) similar to the one in the Vatican.
Hennessey is a strange protagonist in that she is largely peripheral to the plot. Indeed, the plot would have been exactly the same if she wasn't in it. Her role is to investigate the Vatican's ossuary, but it is Bersei who makes all the discoveries and drives this side of the story along. She seems to be there as a plot device for a sequel. The book's ending is not conclusive (the only surprise throughout the book), the question of the identity of the occupant of the Vatican's ossuary is not conclusively revealed or closed, although strongly hinted at and questions remain as to what to do with a sample of the bones' DNA, which has strong healing powers. Here the plot for a sequel is mapped out as Hennessey is suffering from cancer of the bone.
All in all I would cautiously recommend it if you enjoy this genre and have nothing else to read.