If you have not read it, the basic idea is that Billy Pilgrim, an American serviceman who witnesses the bombing massacre of the German city of Dresden, has two personal peculiarities. One is that he becomes "unstuck in time," meaning he travels back and forth to segments of his life unwilling. The other is that he is later kidnapped by a race of aliens who see all moments of time at once. Neither is related.
What it does well: At one point, caged in an alien zoo, Billy has a chance to study alien books. The explanation the aliens give him may as well be a description of Slaughterhouse-Five:
Billy couldn't read Tralfamadorian, of course, but he could at least see how the books were laid out--in brief clumps of symbols separated by stars. Billy commented that the clumps might be telegrams.
"Exactly," said the voice.
"They are telegrams?"
"There are no telegrams on Tralfamadore. But you're right: each clump of symbols is a brief, urgent message--describing a situation, a scene. We Tralfamadorians read them all at once, not one after the other. There isn't any particular relationship between all the messages, except that the author has chosen them carefully, so that, when seen all at once, they produce an image of life that is beautiful and surprising and deep. There is no beginning, no middle, no end, no suspense, no moral, no causes, no effects. What we love in our books are the depths of many marvelous moments seen all at one time.
Slaughterhouse-Five is, by virtue of Billy's unstuckness, a Tralfamadorian book, one that collects a series of moments in Billy's life and shuffles them so they become like these "clumps of symbols." In that way the structure of Slaughterhouse-Five cleverly emphasizes its themes. I believe that Vonnegut wants us to notice this similarity.
But this is also problematic. The Tralfamadorians insist that there is no particular relationship between these moments, but that they create a singular impression when taken together, and yet you can't say that about this (or maybe any) book. Fifty Booker Billy (not Pilgrim) notes a parallel he finds between a character's cruelty to a dog and man's cruelty at Dresden, but in Tralfamadorian books, there are no parallels. In fact, the very way that Billy's unstuckness parallels the Tralfamadorian experience of time ensures that Slaughterhouse-Five is not Tralfamadorian. We go on looking for patterns, partly because that is our human instinct, and partly because Vonnegut quite clearly puts them there.
Fifty Booker Billy writes that he sees a line between the "destined and random" and the merely "cruel." Passages like this make me wonder:
"It had to be done," Rumfoord told Billy, speaking of the destruction of Dresden.
"I know," said Billy.
"I know. I'm not complaining."
"It must have been hell on the ground."
"It was," said Billy Pilgrim.
"Pity the men who had to do it."
"You must have had mixed feelings, there on the ground."
"It was all right," said Billy. "Everything is all right, and everybody has to do exactly what he does. I learned that on Tralfamadore."
I have a hard time finding Vonnegut distancing himself from this fatalism, which I find very bleak. Nor do I agree that if this were true it would make everything "all right." But it seems to give Billy a sense of calm acceptance, and, as Fifty Booker Billy has noted, it's not hard to wonder whether Slaughterhouse-Five was written in order to give Vonnegut, who also was present at the bombing of Dresden, a similar way of coping.