"Prostitution?" Does it actually say that in the catalog copy? Who writes that $#%$?
If I wrote a book called The Book of Vile Darkness, I'd fill it with the most hideously evil spells, feats, prestige classes, magic items, artifacts, monsters and NPCs that you'd ever want to put in a D&D game. I'd include rules for the benefits evil cultists get from sacrifices, new poisons, diseases, and so on.
I'd also include plenty of DM advice on running evil villains, villainous plots, evil organizations, and so on. I'd include a little, but not a lot of, discussion on running evil PCs.
Oh, and did I mention that the "monsters" that I'd put in there would include all the major archdevils and demon princes? And their various minions? And those that revere them almost like gods?
That's what I would do. If I wrote a book called the Book of Vile Darkness.