Longer than a short story and shorter than a novel, Daisy Miller is a novella. While reading the story, it is worthwhile to consider that before the novella was published as a complete text, readers first encountered it serially in a magazine over the course of two months
The novella belongs to the genre of literary Realism, as it is made up by the everyday conversations and activities of James's characters. As can be expected in a literary realist text, the narrator dwells on ordinary details like minute features of a given setting or people's clothing. During conversations, the reader not only receives extended dialogue, but also the characters' accompanying facial expressions and body language.
Although the tone and mood are marked by consistent playfulness, there is nevertheless something tragic to the narrative. This is not simply because Daisy dies at the end but, more importantly, because she and Winterbourne never manage to develop a serious relationship. They both like each other very much, and yet they increasingly confuse and hurt each other. Even when they are in the same place, they usually seem to be missing each other.
At Vevay, where the only people scrutinizing them are Mrs. Costello and the courier Eugenio, Winterbourne is able to be his more authentic self with Daisy. Mirroring her spontaneous, open behavior, he seems on the cusp of some valuable character development thanks to his new friend. In Rome, where Mrs. Walker and her fellow Americans are constantly watching, Winterbourne feels limited by propriety in his interactions with the ostracized Daisy. Their conversations become less playful than they were at Vevay, as Winterbourne devotes much of his time with Daisy to warning her about the consequences of her social blunders. What makes the ending feel tragic is that it's only after Daisy dies that Winterbourne feels he understands her. He returns to Geneva without having changed much at all.