Taboo is fine when it stays in the boundaries of good taste and morality, for example: scenes of gore (for example Higurashi) may be fine for some, but for the others its just plain disgusting.
In short, it depends on personal taste, its you deciding if you want to read something or not.
Personally, as long as it isnt just plain crap, incest is fine,gore is fine, but i absolutely hate rape.