So I was reading a post explaining a quote on ELU when I saw this sentence: "Caliban is indeed a character in a Shakespeare play."
So my question is: Shouldn't the suffix 's be used on Shakespeare in this sentence? Wouldn't "Caliban is indeed a character in a Shakespeare's play" be the grammatically correct form?
If I'm wrong, could someone explain in a simple way to me when I should and shouldn't use the suffix -s, or redirect me to a post addressing that issue?
Btw, the sentence was found in this post: https://english.stackexchange.com/questions/175668/an-explanation-of-the-preface-in-the-picture-of-dorian-gray.