Graham Hancock and Robert Bauval have produced a number of books, separately and together, on various subjects of esoteric interest, primarily dealing with the possibility of a hitherto unknown civilization having existed before the last Ice Age. These books are usually diverting and often thought provoking, as is Talisman, even when the reader fails to be convinced of the overall thesis of the authors.
Talisman supposedly describes the centuries old history of a secret faith which has surfaced time and again in human history. The sections which deal with the early Christian gnostics and the Cathars are very well done and provide some intriguing information about the parallels between those groups of which I had not previously known. I also found the segments dealing with the Templars and their links to the Freemasons intriguing, as will other readers who have enjoyed such books as Holy Blood, Holy Grail, The Messianic Legacy, and others of that ilk.
Where I found my interest and credulity flagging were the sections dealing with the numerous references to Ancient Egyptian religion to be found among the French Revolutionaries and in the supposed Masonic symbolism to be found in cities like Washington and Paris. Egyptian references during the French Revolution make sense when you remember that the Catholic Church was considered an arm of the French monarchy, and that therefore anti-monarchists would also be anti-Church and seek to replace it with symbols of other faiths. Also it is well known that Freemasons were actively involved in the Enlightenment Period and that many early US leaders were (and continue to be in the present era) Masons. However, I tend to be skeptical of maps detailing straight lines linking different sites. (It has always been my observation that if you draw lines long enough and in enough directions you can link up just about anything you want to.)
I was also somewhat puzzled by the references to 9/11 that are tagged on at the end of the book. While Al Qaeda members certainly appear to be gullible enough to swallow the idea of a huge Jewish/Masonic conspiracy against them, I don't believe that Osama bin Laden chose to destroy the World Trade Center because the towers had Masonic significance!
All in all I can say that this is an entertaining book which will provide a lot of interesting information about Gnosticism, Catharism, and other assorted heresies and the Catholic Church's responses to them, but unfortunately mixed in with this material is a lot of poorly sorted out and ultimately irrelevant data.