Looking over stuff I've played, the best fits that are also pretty solid games are:
Deus Machina Demonbane (because "Book Heroine" is not a very common tag, and Al has far and away the best route anyway)
The Steampunk series (the romance in Sekien no Inganock is definitely a little off-kilter)
There's an incest route in Chrono Clock too, I suppose, and it's a pretty good game to begin with, but it generally feels pretty straightforward, so I doubt it's what you're looking for. Do have to agree with skrewball's suggestion of Funbag Fantasy, though — it's certainly more interesting than a run-of-the-mill nukige.