I'm always fascinated at the diversity of responses people give whenever this topic comes up. It really seems like people have wildly different expectations for a book of this nature, moreso than they would for a book on almost any other topic.
Several people expressed the opinion that "mature" was very different (and even removed from) focusing on sexual materials; presumably, this indicates a certain style of how a book like this would be written (e.g. World of Darkness) more than what it's actually about.
Others have mentioned that D&D is simply a bad medium in and of itself for sexual subject matter. I can't fully disagree with that, as D&D is at its heart a tactical combat game. Trying to wrench its focus outside of that does feel jarring, bringing the game's focus somewhat out of context.
A number of posters simply said they don't have any practical use or such material, though they have no problem with it. That's inevitable, as every book has a certain demographic of role-players that just won't care for that particular subject or genre - I'm just glad there aren't as many people saying that this particular area shouldn't be explored at all.
Specifically regarding the
Book of Erotic Fantasy, my opinion is that it's "failure" (and I agree with Aus_Snow in that we can't be sure if it failed or succeeded from a sales standpoint) wasn't due to any particular flaws of game design (it needed errata, but so do a lot of books), nor due to the unconventional artwork (it was very different, but not terrible in and of itself), but rather because it presented the material overtly, without any particular way to tie things into an existing game.
Other than a handful of barely-developed new organizations, deities, and some monsters (and I found the monsters to be quite lackluster), the BoEF made itself too stark in what it offered. The new crunch had a consistent flavor (e.g. it was sexual) but there was no in-game mechanism for why that'd suddenly start appearing in your games. It'd be weird (to say the least) if PCs were told they could suddenly take feats like Tantric, or enemy spellcasters started using spells like
orgasmic vibrations on your characters during a fight.
I think that if you're going to incorporate such material into your game, it shouldn't just suddenly be added with no in-game rationale - that's the gaming equivalent of being in, say, a classroom when somebody opens the door, realizes they have the wrong room, and leaves; it's awkward, embarrassing, and doesn't accomplish anything.
Contrast this with if the person entering the room has a reason for doing so (or was there in the first place); if there's an in-game reason for sexual materials suddenly becoming so prominent, then it makes more sense, especially if it's localized to a particular place/group/adventure. It's less "why did the necromancer use a spell that switched my character's gender? He's a freaking necromancer fer cryin' out loud!" and more "Remember when we assaulted the temple of the Goddess of Pain and Pleasure? Those priestesses fought seriously dirty, using sex-based spells like that." That's why I much prefer
Sisters of Rapture to the BoEF, as it's lighter on the sexual crunch, and ties almost all of what it does present to the new cult introduced in the book.
...well, that and it has illustrations of naked women, rather than photoshopped pictures.
)
