I've seen writing books on characterization, plot, world-building, conflict and probably 1000 other topics. But are there any good books that focus on how to write good erotica or romance? If it's a book you've used, please say why you'd recommend it.
I'm not a romance writer, but because I hate orphaned questions, I can offer you a link which I found interesting. (Well, you probably know it.)
It's not a book, but articles from different authors to the subject.