For the first three quarters or so I thought this was probably the best Le Carre I've read so far. Then some things happened that I didn't believe, and all bets were off.
Overall the story was good - following the middle part of the end of George Smiley's career - but I've noted something about the writing in these books now that bugs me: the point of view wanders. Sometimes it's omniscient, sometimes it's from the perspective of a single character, sometimes it's from the perspective of some review or report written after the fact, and so on. The changes aren't clearly delineated, and (in fact) I think I saw changes of these sorts mid chapter.
I'm not sure what to make of Le Carre's take on his characters either. No one is presented in a great light, but perhaps that has to do with the nature of the spy business.
In any case the Karla trilogy was very popular and makes for interesting reading, even if there are some issues with the writing.
Carre simplest fictional sky master.