It might help to understand Vonnegut's wartime experience. Unreal written weirdness abounds, yet there is quite a bit of real world context to this book.
If you choose to stick with it though to the end, see if you can locate the climax of the story. It will be better if you don't research this until you are finished reading. If your answer is different from what Vonnegut said, well, he makes a good point.
If you choose to give up without finishing, allow me to suggest Hocus Pocus as an alternative. It's wrapped in Vonnegut's satire and freakish writing style and all, while remaining a straightforward story that Slaughterhouse Five is not.