What is the author's style in The Sirens of Titan by Kurt Vonnegut?

The story is told largely in the past tense and in the third person voice. The exception is when the narrator addresses the reader directly, when the language changes to the present tense. Framing the story in this way gives Vonnegut flexibility to provide background information directly, without having to use expository techniques within the story itself. It also supports the pretense, announced at the very beginning of the book, that the events described actually happened from the point of view of the narrator.