Series /
movie?
I find it funny that whenever I'm watching one I'm yearning for the other. The series has a lot more content and scenes that draw it closer to the source material, the film's line-up in general is better (both are good in this respect) and it has more style. My brother thinks the series shows its age a bit.
The book is really worth a read. John le Carre really knew how to write technically a spy thriller that's really all about the characters rather than some convoluted "got to achieve X before Y happens" which in my experience is the staple of the genre.