The first and second chapters share many formal and structural similarities, which are also present across the entire novel.
The most characteristic structural element of Slaughterhouse Five is the book's use of very short sections. Sections are sometimes as short as two paragraphs in the first and second chapters, as they are in the rest of the novel.
Another formal characteristic of Slaughterhouse Five is the broken time-line or non-linear narrative. Events take place out of order, yet are usually topically or thematically related to one another so that a sense of cohesion remains connecting each section, though the connection is often not a logical/time connection.