The Holy Blood and the Holy Grail (retitled Holy Blood, Holy Grail in the United States) is a controversial book by Michael Baigent, Richard Leigh, and Henry Lincoln, which was based in large part on Pierre Plantard’s Priory of Sion.
The book was first published in 1982 by Jonathan Cape in London, as a follow-up to a BBC TV documentary on the series Chronicle. A sequel to the book, called The Messianic Legacy, was published in 1987. The original work was reissued in an illustrated hardcover version in 2005. One of the books, according to the authors, which influenced the project was L’Or de Rennes (later re-published as Le Trésor Maudit), a 1967 book by Gérard de Se`de.
In summary, the authors argue that there is evidence that Jesus married Mary Magdalene, had one or more children, and that those children or their descendants emigrated to what is now southern France. Once there, they intermarried with the noble families that would eventually become the Merovingian dynasty, which is championed today by a secret society called the Priory of Sion.
An international bestseller upon its release, The Holy Blood and the Holy Grail spurred interest in a number of ideas related to its central thesis. Response from mainstream historians and academics, however, was nearly universally negative. Professional historians argued that the bulk of the claims, ancient mysteries and conspiracy theories presented as fact, are pseudohistorical. Nevertheless, these ideas would then be fictionalised by Dan Brown in 2003 in his runaway best-seller novel The Da Vinci Code, even using Richard Leigh’s last name for the character Leigh Teabing’s first name and Michael Baigent’s last name, scrambled, for Leigh Teabing’s last name. (quoted after Vikipedia).
Here is the cover illustration for the British edition: http://upload.wikimedia.org/wikipedia/en/b/b8/The_Holy_Blood_and_the_Holy_Grail.jpg