I really enjoyed the movie, simple plot, great story, good cast. But a different story is being told in the book. It's far more complicated: one really has to concentrate and read carefully every sentence in order to understand what's going on. I'm almost done reading it and I still don't have a clear picture on who's who. There's so much confusion and the story is so complicated it's almost annoying. I also don't like the long dialogues between Jason and Marie. They slow the book down enormously. Reading this book should be a heart-pounding experience, but instead it becomes incredibly boring.
Speaking of Marie, I don't like her character either. All that happens between Jason and her, seems so unlikely it's almost funny and ridiculous. She is portrayed as this superwoman, sometimes casting a big dark shadow upon Jason's figure (which should be the strong one). She practically leads him by hand, tells him what to do.
Jason is supposed to be very bright, very strong...a superman without memory. Instead he seems like a frightened child, who needs help from a woman in order to understand what's going on. He therefore becomes weak and dependent upon others. It's not the Jason I saw and liked in the movie.
The plot also never seems to go past Paris, everything is being played out there. I think this book lacks on mobility and tension. I wouldn't recommend it to someone who's looking for the same story of the movie.