Not sure where all the 5 star reviews are coming from. I have read all of Harris's books, and woul dgenerally rate them all without an exception I can think of as 4.5 or 5 out of 5.
But this one, which is an attempt at a Le Carre clone, just didn't do it for me. the story seemed slight, relatively few twists or intrigues and een the setting wa sa bit dull. So much so that I did not get past 75% of the book. As much as I felt sad for not completing it, after putting the time in, it just didn't grip me. Maybe the last 25% was stunning. But it woul dhave had to have been stunning to warrant more stars.
I gve it three based on the fact that I know Harris writes great books - so maybe it was just me, but I don't think it was.