I think this could be applied to pre-existing SFF titles too in order to fully prepare readers for what's in store for them between the covers. Neil Gaiman's American Gods: Brooding: TICK / Epic: TICK / Spiders: tick / Gods: TICK / Sexy: tick.
I bought this book online wanting to read some of Gollancz's Urban Fantasy and as Neill had just released her latest in the Chicagoland Vampires series, Twice Bitten, I thought an obvious place to start would be at the beginning. If I'd have seen this book in a shop first I might not have bought it. I'm a cover-judger and I think that publishers can have faith in their readership to not be put off by a book because they weren't expecting the vampire novel to be that *picture of a bat*.
The other elements of the design are standard Urban Fantasy fare. Photo of a girl: TICK / cityscape: TICK / weapon: TICK / absence of fantasy: TICK.
The story begins with Neill's female protagonist Merit joining the ranks of the not-so-undead, so I will now go and read my *smiley face with fangs/lips/picture of a bat* new book, suspending judgement in the hope that there are a few narrative surprises that can't be explained with a few mobile-friendly smileys.