Readers may disagree about key themes. Support your assertions. To avoid plot summary, you should be sure that details are not offered for their own sake but in support of some assertion in your essay. Familiarize yourself with some of the main genres , or literary types, and label individual works appropriately. Works of fiction include novels, short stories, novellas, etc.
Poetry includes such subgenres as epic, lyric, sonnet, etc.
Plays or dramas are normally intended to be acted on a stage. Essays are relatively free discussions of topics, but normally without characters, plots, or versification. Be prepared to discuss biographical and historical backgrounds.