Been a fan of LeCarre's (David Cornwell) writings since I was a teenager. Tightly written, and a command of the language that evokes powerful images as your read. Now.... the BBC series with Sir Alex Guiness (RIP) is a hard act to follow. Regardless of the critic's fawnings over the latest tribute to what many call the "ultimate" spy novel, I would strongly suggest that before watching the flic, READ the book. Or at the least find the DVD set from BBC's series as it is quite accurate, if but detailed.
Here's the rub, however. It took almost 9 hours of BBC recording in the series to basically capture what LeCarre wrote. Now we have a "modern" movie that, at least in theory, is supposed to be a "definitive" interpretation. That folks, will be difficult. Notwithstanding the actors' abilities to do justice to the characters, etc. There's going to be a shallowness, almost 2-dimensional panorama (to the film's detriment, of course) of the tale to be told.
Unfortunately, reading a book is fast becoming a lost art in todays world which demands "thumbnails", and nothing longer than 180 minutes of celluloid distraction from our busy, multi-tasked and drone like lives.
Read the book, watch the BBC version, then see the movie..... It's worth the extra effort to see what a good story should be; hopefully the directors will get it right.