Originally posted by Lestov16
How do you get permission?
Copyright infringement in books only ever comes up when one writer thinks another writer has stolen something from him. And because fiction is so derivative (it varies according to genre, but as a writer I steal things all the time) a writer has to pick their battles, so they usually only sue when it's blatant (look at the Russian Harry Potter ripoff for an example of how far you usually have to go to attract a lawsuit).