The novel is simple in syntax and sentence structure, part of Vonnegut's signature style. Likewise, irony, sentimentality, black humor, and didacticism are prevalent throughout the work. Like much of his oeuvre, Slaughterhouse-Five is broken into small pieces, and in this case, brief experiences in one point in time. Vonnegut himself has claimed his books "are essentially mosaics made up of a whole bunch of tiny little chips...and each chip is a joke." Vonnegut also includes hand-drawn illustrations, a technique he repeated in his next novel, Breakfast of Champions (1973). Characteristically, Vonnegut makes heavy use of repetition, frequently using the phrase "So it goes": as a refrain when events of death, dying, and mortality occur or are mentioned, as a narrative transition to another subject, as a memento mori, as comic relief, and to explain the unexplained. It appears 106 times.
The book has been classified as a postmodern, meta-fictional novel. The first chapter of Slaughterhouse-Five is written in the style of an author's preface about how he came to write the novel. The Narrator introduces the novel's genesis by telling of his connection to the Dresden bombing, and why he is recording it. He gives a description of himself and the book, saying that it is a desperate attempt at scholarly work. He ends the first chapter by discussing the beginning and end of the novel. He then segues to the story of Billy Pilgrim: "Listen: Billy Pilgrim has come unstuck in time", thus the transition from the writer's perspective to that of the third-person, omniscient Narrator. (The use of "Listen" as an opening interjection mimics the epic poem Beowulf.) The fictional "story" appears to begin in Chapter Two, although there is no reason to presume that the first chapter is not fiction. This technique is common to postmodern meta-fiction. The story purports to be a disjointed narrative, from Billy Pilgrim's point of view, of being unstuck in time. Vonnegut's writing usually contains such disorder. He apologizes for the novel being "so short and jumbled and jangled," but says "there is nothing intelligent to say about a massacre."
The Narrator reports that Billy Pilgrim experiences his life discontinuously, so that he randomly lives (and relives) his birth, youth, old age, and death, rather than in customary linear order. There are two main narrative threads: Billy's wartime period (interrupted with episodes from other periods and places in his life), which is mostly linear, and his discontinuous pre-war and post-war lives. Billy's existential perspective was compromised by his witnessing Dresden's destruction, although he had come "unstuck in time" before arriving in the city. Slaughterhouse-Five is told in short, declarative sentences, which suggest the sense of reading a report of facts.
The first sentence says, "All this happened, more or less." (In 2010 this was ranked No. 38 on the American Book Review's list of "100 Best First Lines from Novels.") The opening sentences of the novel have been said to contain the aesthetic "method statement" of the entire novel. The author later appears as a sick fellow prisoner in Billy Pilgrim's World War II. The Narrator notes this saying, "That was I. That was me. That was the author of this book." The story repeatedly refers to real and fictional novels and other works of fiction; Billy reads Valley of the Dolls (1966), skims a Tralfamadorian book, and participates in a radio talk show, part of a literary-expert panel discussing "The Death of the Novel". Kilgore Trout, whom Billy Pilgrim meets while operating a newspaper delivery business, can be seen as Vonnegut's alter ego, though the two differ in some respects. Trout's career as a science fiction novelist is checkered with thieving publishers, and the fictional author is unaware of his readership.