‘From Russia with Love’ is very close to the book. The others use the title and little else.
To me shifting the villains from the soviets to spectre was a major change. Some say On Her Majesty’s Secret Service is the one closest to the book in plot. Goldfinger and Thunderball were pretty close too. The movie that really departed from the book for the first time was You Only Live Twice.
The first four (Dr No, FRWL, Goldfinger and Thunderball) are pretty close to the books. They have the same plots and characters (aside from bringing in SPECTRE and dispensing with SMERSH). IMO, Goldfinger the movie is better than the book. All the rest, aside from On Her Majesty's Secret Service have little to do with the books.
My favorite book was Moonraker, and the movie had nothing to do with that book. My second favorite was Live and Let Die. The movie only barely resembled that book, and one of the most suspenseful sequences was used in the dreary License to Kill. Much of the recent Casino Royale was drawn from the book. I rate Casino Royale the movie right behind the first three Connery films.
I should probably re-read the novels. One thing I liked about them is that they are gripping, and generally run around 200 pages or less. Too many of today's writers could learn a thing or two from Fleming about editing.