When I read a novel set in a city I know well, I must see that the writer knows the city as well as I do if I am to take that writer seriously
Novel is separate from the word set,
Set is a modifier in this sentence, meaning that the plot of the novel is occurs in the city I know well.
The sentence means, that "If the author of the book does not reveal that he knows well the city, he is describing in the novel, I am not going to take seriously this author and his book."
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Never give up,,,