Not the worst novel, but likely the worst of the films.
There's just something about Las Vegas.
Spectreville!
Prolly the best of the novels, an Eric Ambler homage, Soviet SMERSH villains including an odious lesbian and of course, the beautiful Tatiana Romanov.
As intermission, a few writerly observations about Fleming follow. In Casino the PoV was only Bond: every sensory detail, every missed clue, even the torture scene.