I liked the book better because somehow seeing them narrowly escape one explosion after another gets a little boring after a while (though somehow it seemed exciting in the book). And the scenes they added were lame, the seminary student who went to the club seemed like an excuse to throw in some scripture that wasn't mentioned in the book. I think if they would have left it like it was in the book and included a little more of the slow stuff that explains the characters (like the hotel scene with Kevin and Sam) and the theological stuff with Kevin's professor I would have liked the movie a decent bit more. Also, I don't like it when movies flash scenes at you for less than 2 seconds and then go back to showing a character's face, that always seems cheesey rather than dramatic or exciting.
Oh yeah, and I didn't like the closure they put on the riddle killer story, I think it was super lame and cheesey that they caught him from seeing a picture of a guy with a camera in a newspaper clipping. Also that he said "I can't stand copycats" was dorky too, and how did he figure out that kevin was actually his own stalker that fast? He figured it out after the first bomb, which was WAY before the cops even suspected it. Also, the bomb in the fridge was excessive and-like the club thing-just added to the monotony of the good guys narrowly escaping explosions.
And lastly, I didn't like the way they took out the stuff with the voice masking device. Even though it works they way they had Kevin playing his 2 alternate personalities, the voice masking bit in the book gave it a chance to slow down for you to chew on what was going on, it's like in the movie they were too afraid to give you any time to think so they just rushed to the big twist at the end. So yeah, the book was better, but the movie was worth watching.