He threatened you to either buy a new book or he would make your uni career hell, one of my mates did it, at the last exam he sent him back 5 times, the last time he went to take the exam the coordiator said “what else have you got to ask to him; he told you everything in your course; [insert name] give me the paper” he signed the paper and sent him off; the prof. Still gave him only 60/100.
I still want to slap that piece of shit.
After that i taught other people in the uni to do that; he tried to mitigate by writing over the printed title of the book; hoping that any tampering would be evident; toluene didn’t touch the toner, so it didn’t work