Simple, Poetic, Pseudo-Technical
Some of the cleanest, most energetic lines in this text are also the most poetic:
I am behind bars.
I am behind bars in a nice new jail in old Jerusalem.
I am awaiting a fair trial for my war crimes by the Republic of Israel. (1.7-9)
The lines add beats to the flow of reading, but they don't interrupt that flow. They also add detail while building suspense. In case you had forgotten, Campbell is a poet as well as a playwright, and he's not above sneaking a little of that flair into this particular text.
When Campbell's not being poetic, though, he's really into trying to sound official. Terribly official: the sentences are formal, almost dry. This hyper-academic attention to detail gives us the impression that this is all Very Important Stuff. At least until Campbell makes a pun.
Here's a snippet from the Editor's Notes that's supposed to be all Vonnegut:
I don't care to argue the point. My duties as an editor are in no sense polemic. They are simply to pass on, in the most satisfactory style, the confessions of Campbell. (Editor's Note.3)
And here is a very serious acknowledgement by Campbell for help with his fictional research:
I am indebted to the Haifa Institute for the Documentation of War Criminals for the source material that makes it possible for me to include in this account a biography of Dr. Jones, publisher of The White Christian Minuteman. (13.1)
Both are examples of how the language is structured to deliver a sense of formality and legal backing. It's almost like the stuffier they can make their writing sound, the more they think people will believe them. Hmm…