"All this happened, more or less."
Kurt Vonnegut begins his novel Slaughterhouse-Five with an autobiographical description of the effect that World War II had on him. He witnessed the carpet bombing of Dresden, Germany while he was held there as a prisoner of war. He reflects on how he struggled to describe his wartime experiences and to relate to his friends who had gone through these struggles with him. In the end, he wrote this book about Billy Pilgrim.
"Listen: Billy Pilgrim has come unstuck in time”.
Billy was a soldier, but he wasn't much of a soldier. He was skinny and weak and he had trouble focusing and he was captured by the Germans before he was even issued a gun or boots. Occasionally, Billy became unstuck in time - traveling to the past or the future to experience different periods of his life before returning to the moment when he left.
On one journey to the future, Billy was kidnapped by aliens and transported to the planet Tralfamador, where he was placed in a zoo for the study and entertainment of the local inhabitants. The Tralfamadorians see the universe in four dimensions, which gives them the ability to perceive every moment of the past and present simultaneously. Because of this, they have developed a philosophy that all that has happened or will happen is unchangeable. They accept as their destiny what they are powerless to affect, and they respond with the simple - almost flippant - phrase: "and so it goes." This phrase follows nearly every mention of death in the book.
This is a science fiction story about aliens and distant planets and time travel. But it is also a war story, chronicling the 1945 Allied bombing of Dresden - a campaign that was successful, but yielded no significant advantage to the Allies. Thousands of civilians were killed in a pointless display of force. More correctly, this is an anti-war story, demonstrating the absurdity of armed conflict.
It is possible that Billy's travels between times and between planets occur only in his imagination - a result of Post Traumatic Stress Disorder, brought on by the horrors of the war; but it does not matter whether or not Billy dreams it all - at least not to the reader and maybe not to Billy. Viewing and living his life nonsequentially helps him to perceive the universe as the aliens do and to adapt some of their fatalistic views and better accept death and tragedy.
The book's non-linear narrative and almost complete lack of a plot might be perceived as a weakness. But Vonnegut takes us through a series of episodes that tie together and he does so with a sparse, informal style that makes for a pleasant journey.
Ultimately, the novel is about fate and inevitability and acceptance of the unavoidable. The Tralfamadorians understood the future and accepted their inability to change it. Billy comes to do the same. Even the horrors of war seem predestined. Those fighting the battles have no control over the events that affect their lives, and the Dresden civilians had no reason to suspect they were a target.
And so it goes.