Personally, the book was a very well written, amazing, thrilling piece that was not brought to justice to the movie. Watching the movie at 12.01 in the morning to see that major parts of the book were left out frustrated me, seeing that it affected the "different" outcome of the movie. There was something to be desired out of this movie, but all in all, it lacked in plot.
For someone who has NOT read the book, I could see how this movie would be seen as inviting and entertaining with its controversy and suspense. However to a dedicated reader who has read it seven times, I did not see the strong connection between the two: both the movie and the novel.
With major characters missing (such as Maximilian Kohler) and the abrupt turn in plot with the survival of the last cardinal in the preferiti, the plot of the movie was slightly strewn thus leading to a different take in the conclusion of the story. The Hassassin too was portrayed as a common white man, compared to that of in the novel where he was portrayed as a Muslim; his motives in the book are predominately based his ties with the Illuminati, however, in the movie, his motives are based on money and seemed more like work than some personal tie to the task at hand.