This will be a review of not just Casino Royale, but of the James Bond books in general. I think that there is a good argument to be made, that the Bond books are the most misunderstood books of all prominent books, because the very subtext that accounts for their enduring appeal is buried so deeply that it just passes most people by.
The best way to understand the James Bond books is to understand the heroines of the books. These heroines are often characterized as being glamorous women who it is Bond's role to save. This is completely and totally wrong. The whole key is that these women ALWAYS have short unpainted nails. They are actors and present an existential challenge to James Bond. In fact the best way to understand Bond is as a kind of existential literature.
Fleming was a writer who had a message that he seemed not to be fully and consciously aware of. He says the same message in every book, and he says it in the same way (with the exceptions of The Spy Who Loved Me and the short story Quantum of Solace, where the same themes are approached from alternative directions).
Fleming is often compared to Le Carre, almost always negatively. This is an unfair comparison in two ways. First of all, Fleming is a great writer and is, along with Lovecraft, one of the two greatest writers of Pulp in history, whereas Le Carre is merely a very good writer. Second, Fleming is not really writing spy literature, he is really writing fantasy in which the hero happens to have the occupation of a spy. As such, criticisms of a lack of realism are about as out of place as they would be for The Lord of the Rings or Alice in Wonderland. I would have thought, that the Bond books wear their status as fantasy more clearly than, say, the Latin American Magical Realists, but this point appears to pass people by.
The next thing to notice about James Bond is that he is pretty clearly a broken person. The thing that I most love about Daniel Craig's interpretation of Bond is that he conveys this point clearly and repetitively in a way that has not been done before. Bond is a kind of broken Nietzchean superhero who has in a way arbitrarily and for what appear to be purely aesthetic reasons, taken on a specific set of values that we are meant to recognize intuitively as a priori superior to competing values. In this he is exactly the same as both the James Bond heroines and villains.
If you read the Bond books critically, one of the things that is most striking about them is how similar in personality Bond is to both the heroines (with a few exceptions) and the villains (also with a few exceptions). Fleming will distinguish Bond from the villains not so much by their actions, which are often quite similar, but instead by things such as the cut of their suit or their taste in luxury watches. These aesthetic choices are meant to be inherently preferable, just as Bond's belief system and set of values is never defended as superior to communism or, ironically, to the vast accumulation of wealth and power that other figures such as Goldfinger are bent on accumulating, e.g. the values of capitalism.
Bond, the villains, and the heroines of the books all have in common that they do not in any way feel bound by conventional morays, rules of decorum or value judgments. All of the major characters have in fact chosen a belief system and a set of values through force of their personal will alone. The other characters have not and this is why those characters are kinds of ghosts within the books and are in some sort of way not worthy of interacting with Bond.
The villains have in fact chosen the wrong values. They are every bit as ruthlessly dedicated to them as Bond, and they will not in any way compromise them just as Bond will not. The women have either chosen the same set of values as Bond or at least a set of values that are not diametrically opposed. They are then worthy romantic interests (this goes only for the main female character in every book). However, Fleming is clear that the heroines Nietzchean superman status means that they are too independent to make the kind of long term bonds necessary for stable relationships. They are not in the next book and presumably, they, like Bond, have moved on unchanged. This is clearest in Casino Royale where the doomed nature of the genuine love that Bond has for Vesper Lynd is clearly spelled out in the events leading up to and following her death.
Also, in this book, Bond fails in his mission in a way that he will not do so spectacularly again, but in staying true to the values that characterize him even at the expense of rejecting a genuine love, he maintains his status as a Nietzschean superhero. A status that Fleming clearly means to be a kind of idealization of how to live one's life and not an actually fully achievable ideal. It is by setting Bond in a fantastic world and not in a world where mundane limits can intrude on this ideal that Fleming can over and over again put forth this ideal in its pure form.
Again, it is a world where the choice of a man's luggage is meant to say as much about him as the choice of his political ideals. It is a morality justified by its aesthete and not vice versa.
But even though it is a fantasy world, it is still a world in which it is not possible to simply always force one's will onto that world. Bond may fail to save the woman, he may fail to stop the villain from getting away, his wife might die, his friend's legs might be eaten by a shark, he may be captured, he may be emotionally devastated by events. But it is still a world in which his maintenance of his own values and beliefs can be specifically maintained through every hardship and peril. In pretty much all the Fleming books, Bond is distracted by doubts, or by emotional weaknesses, and in every book Bond overcomes these by simply pushing them away.
In other words the Bond books represent a kind of practical existential ideal. It is not an implausible solution to the practical problems of our world that Fleming is unconsciously advocating and it appears to be what he attempted to practice in real life. But it is a difficult solution that he advocates none-the-less.