I read fics that hold my interest. For me, if the author makes it believable, I'll read it. The only things I don't read are incest and bestiality and fics that glorify rape.
I even read a lot of the HG/SS fics, not because I ship that pair, but there are some writers who write marvellous stories in that ship. (Also,some of the archives that host that pairing also have requirements as stringent as FA for grammar, canon etc.)That ship also has quite a few writers who stories I would rather not read.
Basically, the author has to make the plot and the story fascinaing and believable.