I don't know why, but I was expecting much more from this book. The movie is so much better ...at everything. From introducing the character (even though we know him very well by now) and his history, to setting this plot and zeal for his job. In here, the story flies past so fast that it never really feels threatening (I know the book is very short, but still) and the subsequent consequences feel forced and underdeveloped.
We also never really see Bond falling in love. He mentions that he wants to quit and marry Vesper, but it never feels genuine, like in the movie.
If you're looking for Bond's origin story, this isn't it. (Does it even exist?) Casino Royale could've been the last 007 novel Fleming had written, and it wouldn't have made a difference. There's barely any action, love, characters, or even story here. The movie goes much more deeper and gives us a better background of the character than Fleming apparently ever intended to do. I think this is the first time I've said this, but the movie is, in every way, superior than the book.
I think we are used to the vivid and detailed creation of characters in movies. In my opinion Ian Fleming is able to do that in between actions and situations. If you read it again with that in mind then I think you will find this novel much more fulfilling than the first time.
Bond saw luck as a woman, to be softly wooed or brutally ravaged, never pandered to or pursued. But he was honest enough to admit that he had never yet been made to suffer by cards or by women. One day, and he accepted the fact, he would be brought to his knees by love or by luck.