Green’s Dictionary of Slang

erotic, pornographic; thus crotch novel, a pornographic book.

1963		H.S. Thompson letter 20 Sept. in Proud Highway (1997) 400: And how about a lewd article or two? Maybe a crotch-eye view of Aspen.
1986		R. Campbell In La-La Land We Trust (1999) 77: The attendant looked up from his crotch magazine, open to the centrefold in which a girl of stunning beauty opened her legs for anyone who cared to ogle her.