How does the narrator's mood change as the story progresses? Why does her husband apparently not see the seriousness of her deterioration?
One of the most important things to remember about this story is that you only have one character's perspective, and this will always, in any story, limit the reader's knowledge about events. Therefore, every detail needs to be considered. With regards to the narrator's condition and her husband's attitude, think about how this house is described, every detail, in every room. The narrator does not become mad or insane as she stays there; she enters the "sanitorium house" already unstable. It is her perception of her husband's actions you are reading.
The husband, John, in the "Yellow Wallpaper" doesn't see the seriousness of his wife's deterioration because following along with the beliefs of that time, he thinks its impossible that a woman could have a mental illness. With so little to do and virtually no stimulation, the narrators mood varies. She realizes that she's starting to see shapes in the yellow wallpaper. She becomes completly obsessed with the wallpaper, and even beleives that her husband is trying to see the shapes before she can. Finally, she succumbs completely to her insanity.
The narrator's mood changes every night, as she becomes every night more and more obsessed with the wallpaper. Eventually, she wants to be the only one to get the truth behind the wallpaper. And in the end, in my opinion, she becomes the woman in the wallpaper, thus meaning she's completely mad. The husband didn't see the seriousness of her deterioration, because she was sleeping nearly all the day, and she was mostly only in her room. And being the age that it was, mental illnesses weren't so frequent, and the narrator was his wife so, basically he couldn't accept that, even if he knew she had a mental illness. Also the narrator's brother was backing up her husband's theories