This is a great question to consider. I would argue that this book does succeed as an anti-war book. Let us remember that throughout all of Billy's toing and froing, the main focus of the story is on Billy as he nearly dies of asphyxiation during the firebombing of Dresden, which was one of the most questionable "atrocities" in the war after the Holocaust. The fact that this act was committed by the allies really makes us think about war and its inherent destructiveness. Many times the narrator seems to struggle to state the purpose of his story, for example saying about his short, simple style of writing:
It is so short and jumbled and jangled, Sam, because there is nothing intelligent to say about a massacre. Everybody is supposed to be dead, to never say anything or want anything ever again. Everything is supposed to be very quiet after a massacre, and it always is, except for the birds. And what do the birds say? All there is to say about a massacre, things like “Poo-tee-weet?”
The war-time atrocities that Billy witnessed were so shocking that the author is rendered silent, and all that is left in the aftermath is birdsong. This is perhaps one of the most open anti-war statements in the book.
We also might like to think about the way in which Billy's life post-war is shown to be shallow and destroyed. Let us remember that the apparent success he enjoys after returning from Europe is only as a result of conditions beyond his control and is only superficial. Perhaps the whole reason that he dreams up his alien abduction is because his life remains traumatised through his war time experiences, and he remains a very powerful testimony of a life that is wrecked by war.