Movie was an excellent adaptation of the book..

It's true that Vonnegut reviving his own experiences and his persistent explanations and discourses are crucial to Slaughterhouse-Five, which are eliminated completely in this film. It's almost a novel within a biography. "So it goes", The Children's Crusade, Billy watching a war movie backwards, what seeing the fourth dimension is like are gone - and, to put it simply, "it's not the same". The one original concept that remains is coming unstuck in time, which is handled predictably through cross-cutting and overlapping voiceovers.
I'm not saying that I loved the book, my favourite Vonnegut novel is Breakfast of Champions, a different matter altogether. I wouldn't call the film a failure period because it was well-filmed; there were beautiful shots of Prague standing in for Dresden, the acting was decent, and I actually liked the added bits and changes, the silly gigantic highway crash included.
The worst part is how trite and unoriginal the film feels without Vonnegut's influence, even though the plot is generally taken from the novel. The novel interested me more because of the ideas like those mentioned above than the characters or the story, and when these ideas are taken out, there's not much except for a fairly intriguing sci-fi/anti-war story. I just didn't get as much out of it.