Having previously read A Small Town in Germany and The Honorable Schoolboy (I think I may have also read Tinker, Tailor, Soldier, Spy, but I'm not sure - how's that for memorability?). I wasn't a huge fan of Le Carreé. He seemed competent enough, but not gripping. I therefore bought this with a little trepidation, but also with strong recommendations.
It's excellent. It twists and turns in a continual low-key but gripping manner. While not wishing to spoil anything, it's the highlight of Smiley's career, in his traditional understated manner. It's like he makes intelligence seem like accountancy, but only if people wrote thrillers about accountancy. Smiley is at his simultaneously ambivalent and driven best. The old characters are back for a curtain call. There's a certain futility which reminds me of, for example, Consider Phlebas, but it's done far better. Highly recommended.