I wouldn't necessarily call this a time-travel movie. It's so much more. It's a great book and movie based on Vonnegut's experiences during the war. It also has the incredible Valerie Perrine, who is not that hard to look at. How many amazing movies did George Roy HIll make?
Editing feels Nicholas Roeg-y but I'm not sure this version really capture the humor in the novel- it might be impossible? I did find effective the scenes after the war with Billy Pilgrim and his family. Those scenes in the "present" captured the post-war meaninglessness quite well but the past and the future seem silly and dated to me but interesting to think how they tried to do it.
The movie doesn't offer anything there's not in the novel and misses many things you can find in the novel. No additional value is created. The main theme of death in the novel is completely erased from the movie. The third person voice is missed. Can't imagine Slaughterhouse-five without the famous "So it goes."
I enjoyed the novel, but the sort of stream-of-consciousness time jumping doesn't really work in a movie. Billy Pilgrim doesn't drive the story; he's more like a passenger. Not harrowing enough to be truly profound, nor funny enough to be satirical. Decent performances, and some of the scenes are well staged, but on the whole, it's pretty mediocre.