the mood or tone of the story is very saad because Tim O'brien made up these lies just to make us feel the same way as he felt
The point of view of the story is a third-person narration, meaning that the person has no direct participation of the story and is just narrating the story as it follows. His job was only to depict the soldiers and the lives and events that had happened when they were in the Quang Ngai province. It proves that the narrator is omniscient, all-knowing person since he knows so detailedly and have great insight and free access to the character's thoughts and emotions, but he only reveals incomplete and half-truth facts about the character and the events relating to the plot of the story.
There was some sort of realism added to the story, as he had managed to describe detailedly the ordinary lives as well as philosophy that confronts the ideals of life instead of fantasizing about them. An example of this literary technique is how well the narrator describe Ted's death, which includes considerable and intricate, straight-to-the-point explanations, his daily actions and movements so well that we believed we were seeing the real person and he is alive and breathing. He also depict a realistic picture of the conditions of the Vietnamese war, drawing attention to the soldier's lives, focusing on small and intricate details that human eyes can hardly portrayed it to be true.
The tone hard to describe, but the book is written in a 3rd person, omniscient style and is written realistically. The realism is heightened by the gripping nature of the setting, a war zone.