The Ministry of Fear by Graham Greene is set against the backdrop of the London Blitz, with overtones of fifth columnists. As such, I found the book provided a fascinating - if perhaps unintended - insight into the wartime zeitgeist. This subject matter is certainly one of its strengths.
Greene's austere, melancholy style - though generally very readable - complements the setting, but also amplifies the somewhat depressing mood that pervades the novel.
The story itself has an amnesic protagonist (Arthur Rowe) - and the reader has to tolerate a correspondingly low level of understanding of just what is going on. At times I found myself skimming lengthy sections (for instance a 1000-word dream sequence in chapter 5), and by about halfway I was ready to give up as I began to find the reading becoming a chore. However, in the nick of time it exploded - in relative terms! - into action, and the plot began to unravel in a more satisfying manner.
Clearly a very good piece of work, though for me it would be about 3.5 stars.