This is an odd instance where I actually read the book a few years before seeing the film and here's the thing I remember thinking the book was a bit limp. I mean this Bond was too busy falling in love and playing baccarat to be badass. The book actually ends with Bond resolving not to be like the other cold agents but to keep to his own morality and keep his distance with women to prevent falling into such traps.
The film was badass. No doubt about it Daniel Craig is a far better Bond than the one I saw in the book but I found myself unable to keep myself from playing spot the difference between the film and the book. That iconic shot that everyone claims was from Doctor No but actually happened by accident was in the book, only it happened later and Bond merely imagined it when he was recovering after the torture.
Here's the thing Casino Royale is a distinctly 'Meh!' book and Casino Royale is definitely a great film but the book does every important thing about the film better. Bond's vulnerability, romance, resolve to overcome his weaknesses, the central romance and the main plot. Each individual thing the film does brilliantly the book does better yet the book is still a worse book than the film is a film.
This seems like such a contradiction but here's what I think is happening, books can without a doubt present concepts and ideas in a stronger, more potent fashion but Bond is a filmic phenomenon. Bond needs to be told in film. Casino Royale is a better book than it is a film but as a book it's weak while as a film, flawed by the adaptation process and a needless sequel hook it may be, it's still stronger.
Oh and when Daniel Craig finally hangs up the tux, he's got my vote to play Sam Vimes.