SMERSH, the villian in the novel has now become SPECTRE. The plot is to have Bond killed in a major scheme while trying to steal a Spektor decoder. The movie`s plot was to have Bond deliver the Lektor decoder to Grant, who would sell it back to the Russians, after disposing of 007.
The character of General G, the main leader of SMERSH in the novel was replaced almost exactly by Ernst Stavro Blofeld, the leader of SPECTRE in the movie. The chracter of Rene Mathis was not used at all, and was a missed opportunity. Most of the locales of the novel were used, except Paris, France. In the movie, this was changed to Venice, Italy.