Before the time of Fakku books, we could nearly judge accurately the quality of a hentai by the number of favorites it has.
I believe this no longer applies. In the case of Fakku Books, less people will be able to read it and someone who hasn't read it probably won't favorite it. Judging its quality via the favorites is no longer reliable.
A rating system (a five-star rating or sumthing), I believe, would fix this and give more security to the potential buyers and assist them in their decision to purchase.