Greene wrote this novella as a means of exploring the atmosphere, characterization, and plot prior to producing the screenplay for the film. It was not originally intended for publication. That these private notes are in fact a compelling piece of prose in their own right says a great deal about Greene as a writer.
Set in Vienna in the aftermath of the Second World War, it tells of how Holly Martins arrives to take up a job for his old friend Harry Lime. He arrives just in time to attend Lime’s funeral. Enraged by the suggestion that Lime was involved with the more unpleasant end of the black market economy, Martins sets out to clear Lime’s name and ends up learning a great deal more than he bargained for.
The constraints of the form (novella and film) mean that the plot is pared down to a minimum and the emphasis is on character and on atmosphere. For all that, the plot is still intriguing enough to sustain interest. And it shows what can be done when real talent is brought together and allowed to innovate.
Perhaps the most enjoyable aspect of the novella is the way in which it captures the seedy atmosphere and frozen streets of the post-War Viennese winter. The political background is captured and explained without clunky exposition. The weariness of all involved, stirred up by the confused energies of Martins, is subtly portrayed.
All in all, this is a classic of storytelling. Read the book (it is usually coupled with The Fallen Idol). See the movie. Enjoy the quality.