What is the book referred to in Episode 4 of Asobi Asobase?
According to this review, the term is slightly mistranslated, and is closer to 'Please Save My Butt', a play on 'Please Save My Earth', which is the series that is garnering the reaction. 

As a side note, Anal Bum Cover is most likely a reference to the Saturday Night Live skit 'Celebrity Jeopary', in which "Sean Connery" reads the category "An Album Cover" as "Anal Bum Cover"