"There are two reasons why a writer would end a sentence with the word "stop" written entirely in capital letters STOP. The first is if the writer were writing a telegram... But there is another reason why a writer would end a sentence with "stop" written entirely in capital letters, and that is to warn readers that the book they are reading is so utterly wretched that if they have begun reading it, the best thing to do would be to stop STOP."
The Hostile Hospital - Brett Helquist, Lemony Snicket

 

Opening Lines