The death of Robert Ludlum was a great loss to the genre of writing that was synonymous with his name, and other greats in the Genre's Pantheon, like John Le Carre. The masters of these books are in no way limited to the two I mention; different readers will all have their favorites.
The reason for the question mark at the beginning of my comments is for several reasons which I believe are important to his admirers from his earliest books, and to those readers experiencing his work for the first time. The final version of this book was completed some three months after the author's death. There is no question that the book is vintage Ludlum, however for his long time readers, evidence of the pen of another will be apparent. There is sardonic dialogue that does not read as his, and the female character, while very well done, is not a pure Ludlum creation in my opinion either.
Nowhere will you find any evidence that this was published posthumously. Every detail on the jacket is in the present tense when referring to Mr. Ludlum. The reason I find this bothersome is that Mr. Ludlum is alleged to have completed 11 additional outlines for books prior to his death. I do not know what constitutes an outline, however it is not a book, and I hope the publishers will be completely candid regarding who was involved in writing these future books. I don't believe anyone can impersonate his style, so whatever may be forthcoming may be great or poor, what they will not be are true Robert Ludlum Novels.
"The Sigma Protocol", is a work that will bring long time admirers back to many of his earlier works. The first work I ever read was his novel, "The Matarese Circle", and this book is almost as good as my initial experience, and other of his works considered to be among his best. The only factor that detracts from this final work is that it is a bit too slick in style. Mr. Ludlum wrote many stories that were complex and cadenced with brilliant speed, however his characters were never those that constantly tossed off quick witted repartee, and endorsed everything they came in contact with by a brand name. Mr. Ludlum wrote books not advertisements.
In spite of whatever intrusion there may have been, this book will make the very short list of Ludlum's best. The tale races all over the globe, and revisits classic locales like Zurich, Vienna, and many others. The World War II element could have been a terrible cliché in a lesser writer's hands. This book portrays a familiar group; however it also legitimizes the suspension of disbelief with real science from recent years. When the book reaches its closing moments it is hard to maintain complete originality, here it was done as well as any could have penned it.
I enthusiastically recommend this book even though its provenance is not completely known. This is also the reason for the lack of the 5th star. There is no way for me to know this; I just don't feel Mr. Ludlum would have wanted readers to be mislead in any manner about his work, to any degree. The bottom line is this is a great read that demonstrates that to the very end of his career Mr. Ludlum was able to create a work that can stand with the best of what he had given readers for decades.