tl;dr Understated and powerful, TTSS is most definitely a successful adaptation and movie of not inconsiderable tension. Brilliantly shot, well acted and subtle. Not for those with a short attention span.
And it's a double bill of le Carre's spy goodness, and I'm not even just copying and pasting the last review on top of this! Actually, the last review I did does impact this one in a very meaningful way. I've read the book; I know the plot and the twists going into the movie. As a story based, to a great extent, on mystery and tension, my foreknowledge of events was always going to affect the way I watched the movie. How closely they stuck to the book for instance (very close) and how they interpret the source material was very much an interesting watch, but also not really appropriate for a review.
What I will say is that the direction is incredibly strong. They translate le Carre's style with incredible skill and capture the understated, repressed atmosphere extremely well. A lot is left unsaid, and dramatic moments are made dramatic through understatement. On top of the skillful and striking directing, there is the plethora of, perhaps inevitable considering the cast involved, great performances. The large cast doesn't allow anyone who isn't Oldman or Cumberbatch to have much time to shine, yet most do nonetheless, making a strong impact with very little.
This is not an all-action affair, a story of talking. Distrust and betrayal are the major themes, and the atmosphere is in the focus far more than the action. This is not a movie that engages you in a normal manner, instead focussing on the slow and mundane side of the business, and it is no less compelling for it.