Ah-ah! Careful! I've never written romance. I don't even read romance. An English romance writer used "Barbara Paul" as a pseudonym for a while, so those romance novels you've come across were all written by her.
Yes, Octavia Butler's writing is social commentary dressed up as SF. There was a rash of that kind of book starting, oh, 30 years ago or more. Butler's a good writer, but not all of the fiction in that subgenre has held up very well. I've not read her vampire book. Right now I'm reading the second book in a series with the collective title Tour of the Merrimack, by R. M. Meluch (the R stands for "Rebecca"). The first book is titled The Myriad and the one I'm reading now is Wolf Star -- rather mundane titles for books that are anything but mundane. Straight SF adventure, idiosyncratic characters, and an absolutely wicked sense of humor. These two books are welcome reminders of how much sheer fun SF can be.
But since mysteries are your first love, I hope you haven't missed Liza Cody's books.