Ben Hartman, an American investment banker, is on holiday when he meets an old friend - an old friend who immediately tries to kill him. Meanwhile, a US government agent is investigating a series of deaths of old men, linked through a secret file. As she makes progress, she is pulled off the case. Their paths cross as they try to solve the mystery.

Weighing in at a somewhat large 535 pages, Ludlum's book is a bit of a monster. The pace starts off quickly, but in a book of this length, it is obviously difficult to maintain and at times, it does become slow and the reader will soon start flicking through the pages looking for the more exciting parts. In terms of plot, Ludlum has succeeded in writing an innovative work, full of mystery and one that was genuinely difficult to work out.

Of course, when it comes down to the solution of the story, Ludlum has taken a great deal of liberties and currently, the medical advances that take place are still a long way from being achieved in real life. However, since reading is all about escapism, Ludlum pulls all these threads together to make an enjoyable novel and a fitting testament to his career, what with this being the first book to be published posthumously and possibly his last ever book.

Overall, despite the slow pace in places, 'The Sigma Protocol' is an enjoyable read which stands above many of the other spy-conspiracy thrillers that are out there. If you have never read a Ludlum before, you could do a lot worse than to try this one, which is certainly an improvement on his previous novel, 'The Prometheus Deception'.