The plot unravels slowly, with much detail, which if forgotten, will leave holes in the story for you later. Each character is thoroughly vetted for the reader. When you've finished the book you will know more about these characters than some of the folks you see everyday.
The name of the book comes from an English child's rhyme which we Americans have our own version.
English Version American Version
Tinker, Tailor, Tinker, Tailor,
Soldier, Sailor Soldier, Sailor,
Rich Man, Poor Man, Rich Man, Poor Man,
Beggar Man, Thief Beggar Man, thief,
Doctor, Lawyer,
Indian Chief.
Why we Americans felt the need to add the last three "professions" is beyond me. I've heard folks say this before when counting or making some type of choice; very similar to how you've probably heard someone use eeny, meeny, miny, moe.
In the case of the book they were not counting or trying to make some random decision, but rather they were trying to figure out who the spy was in the Circus, or what we know as the Secret Intelligence Service (SIS), or MI6, in Britain. The titles were assigned to the suspected spies so that when it is found out who the spy was, it could be communicated without fear of tipping them off.
Throughout the book you are subjected to classic storytelling of past events by the characters trying to pull together their memories to help in the investigation.
While the end of the book wraps quickly, it also does it cleanly without leaving loose ends.
An interesting note about the book is that it's based on a true story the author experienced while he worked for MI6. There really were Russian moles planted in the Circus. The investigation went very much along the lines of what's laid out in the book. There really weren't any martinis. Although there does seem to be an abundance of sherry and scotch in its place. Cheers!
So with all of that said, I know it was a book worth reading for myself because today I have found myself continuously thinking over parts of it, trying to recall bits of it and "flipping through the pages" of my nook to reread sections. I have a lot of books that I've read and reread over the years, but I'm not sure of the last one that made me want to sit down and go back through it so immediately. I take this as a sign of a good book.