I remember watching something that stated once one of the two Dalton flicks (can't remember which offhand) was the first Bond movie not based off one of the novels. However then when I started reading details on the movies and the novels (I've never actually read the books). About half of the films--especially Moore's--took the titles and came up with a completely different story, so really they've been writing original James Bond stories with nothing to do with the books as early as Roger Moore. In general, plot-wise Connery's movies were closer to the books (Thunderball itself was written by Flemming specifically to BE a movie, so IIRC was the closest adaptation of all of them).
That's not to say I thought Moore was all bad for doingthat, either. For Your Eyes Only is one of my favorite Bond movies (AND one of my favorite Bond Girls in Carole Bouquet. I also loved the VERY young Jane Seymour in Live and Let Die). One of the best "henchmen" out of all the movies was Jaws, who was largely invented for the movie version of The Spy Who Loved Me.
So yeah, the movies largely stepped away from the books, but I don't think it's been all THAT bad.