If by ‘formal’ you mean that your essay will be academically assessed or published, then it would be inappropriate to include a spoiler warning. What if I made a piece look amateurish?

Spoiler warnings are suitably considerate in the perfectly legitimate realm where enthusiasts discuss a text and people primarily hope to enjoy the plot. When I am chatting about a text in the pub, I am speaking in this way as an amateur or enthusiast, and I strive not to reveal plot points.

When writing academically-oriented material, that would not be an appropriate consideration. Why? I would look amateurishly clumsy if I were to write about Hamlet while coyly skirting the fact that (almost) everyone dies by the end. I expect readers to know the text we are discussing. “If their primary concern is enjoying the plot, then they have simply selected an inappropriate piece to read.”

If some people still read books, we must choose to write as avid fan or academic, depending on circumstance. Different types of material work differently. What

are some examples?