From Russia with Love is actually one of the truer Bond films to it’s book origins. However, there are still several differences.
In the novel, Bond’s enemy is SMERSH, a Russian counterpart to MI6; and their plan to humiliate and kill Bond is, in part, revenge for their operatives (Le Chiffre, Mr. Big and Drax) in earlier novels. However, as the movies were made out of order, and SPECTRE had already been established in Dr. No, it was decided to once again use SPECTRE (and having the film debut of Blofeld, his face hidden but with his iconic white cat-an invention for the movies)-and for the plot to be revenge for Dr.No. The villanous characters of Rosa Klebb and Kronsteen are retained though, although Klebb is an ex-member of SMERSH in the film.
The bait for the plan in the book is the SPEKTOR decoder, but since the villains in the movie was called SPECTRE, the name was changed to LEKTOR, probably to avoid confusion. SPECTRE also plans to take the LEKTOR from the Russians; whereas in the novel they’d just bring it back to SMERSH.
The film also adds two action scenes after Bond leaves the Orient Express train, one with Bond evading a SPECTRE helicopter (Similar to the Hitchcock film “North by Northwest”) and also fighting off a small SPECTRE boat fleet set to capture him, by throwing his own boat’s fuel in the water and then igniting it with a flare gun.
The ending is somewhat similar, but with a different outcome. In the film, Bond faces off against Rosa Klebb, and nearly gets stabbed by her poisonous shoe knife, but Tatyana, the Bond girl, is able to shoot her before she does. In the novel, the opposite happens; Tatyana is not present, and Bond actually is stabbed and poisoned, although his French police friend Mathis is able to discover Bond in time, although Bond is clearly still very ill, ending the novel with a bit of a cliffhanger, that will be continued in novel order with Dr.No (This originally, oddly enough, was to be the death of Bond in the novel canon, but Fleming decided to go ahead and continue.