I read this book ages ago, when still a teenager, and recently I was happy to discover that "The eye of the needle" really didn't age at all.
This fast paced and quite violent story is about the last German spy still operating in 1944 in Great Britain. Although this is pure fiction, it is a very good read, as the author did his best to make the story stick to the reality of WWII (even if in 1944 the Home Guard was certainly better armed than described here).
The "hero" of the book is a VERY bad guy, but it is impossible not to feel at least a little for him, as he is trying to escape the tightening noose, with a vital piece of information - he is totally alone, very far from home, in a totally hostile place and faces certain death at the slightest mistake or weakness. The way in which he deals with all the adversities forces some respect. His final fate is very surprising and gives this novel a flavour rarely seen in spy stories.
This is a really good book for holidays or a long rainy weekend - I enjoyed it mightily. Ken Follett wrote some good spy novels later - but this is his first and best, no argument there.