Yaar you have to watch the last one "Quantum of Solace" (maybe you did). You could make sense of the whole movie at the end, but to keep track of the plot while watching it was too difficult.
Same with the Matrix movie, the first time I watched it.
Quantum of Solace is sequel to Casino Royale... you can't understand the movie until you had watched the first one,.. but as you can't see the movie without subtitles .. you can watch it without knowing the first movie.. :D