Probably the best Gabriel Allon novel to date. This novel was really a twofer. There are two separate story lines in this book. To top that off, there is a good twist that adds another element of enjoyment to the story.
Hopefully you have long ago discovered Daniel Silva and the Allon series. If so, you know how great he writes. If you are not familiar, start at the very first in the series so you can truly appreciate the development of this series. You can read them out of order but you will sometimes be wondering what you have missed.