"The Confessor" is the third book of the Gabriel Allon series and in my opinion it's the best so far. However, I believe I would've enjoyed it more if I hadn't read "The English Assassin" before.
Someone is assassinated --> Shamron involves Gabriel in the murder case --> it becomes clear that the victim was killed to prevent him from revealing an organization's involvement in the Jewish holocaust during WW2 --> someone central in the plot is targeted by a notorious assassin --> the threat is solved, but not by Allon -- it fits like a glove for both "The English Assassin" and "The Confessor". Most of the characters may be different and they may be travelling to different cities, but I had a constant feeling that I'd read it before.
Also, once again Allon is irrelevant to the story climax, which is a bit irritating. Had he not been there and the outcome would be the same, which is something that also happened in the first two books.
However, it's a fun book to read because it keeps a very high pace, the Catholic Church behavior during WW2 is a captivating theme, and there are also some very tense moments, such as the Rome shootout and the synagogue speech.
+: pace, tension and subject; believable plot from start to finish
-: unoriginal storyline; once again Allon is a non-factor in the book climax
=: If I hadn't read "The English Assassin" before, I would rate it 4 out of 5; even so, "The Confessor" is a book that thriller fans will certainly enjoy