Behold:
Dust City, Robert Paul Weston (Razorbill, 2010)
Not bad, not bad. The "KILLED" jumps out at you, which is awesome. (Not that I'm being morbid or anything...) This sets up the protag (a wolf, and son of a murderer) and suggests that this'll be some kind of twisted fairytale. It's kind of long for a logline, though.
Wolves, Boys & Other Things That Might Kill Me, Kristen Chandler (Viking, 2010)
Here we have an excerpt. (Click for a larger image if you can't read it.) Does it do the trick? I think it does in terms of establishing characters and topic (Virgil's the love interest and wolves are on the menu), but I don't think I'd buy this if I hadn't read the summary. It's just not very intriguing.
Dark Life, Kat Falls (Scholastic Press, 2010)
Ooooh, I love the conflict in those six words. First of all we have "behold", hinting that the Deep is something to revere. BUT... it's also dangerous, according to the "beware". And look at that textured blue background. So pretty!
The Girl in the Steel Corset, Kady Cross (HarlequinTeen, 2011)
The curlicues of the font are gorgeous and match the front cover's title font to a T. However, I have issues with the second part of the text. It sounds almost seductive, which Finley (the girl talking here) isn't. And I wouldn't say the story is really focused that much on her "secret side".
And my favourite...
Blood Red Road, Moira Young (DoubleDay Canada, 2011)
Besides that single period, there's no punctuation. And it just lends this a, a kind of, an almost breathless quality. Not in the valley-girl way, more like your heart's stopped. You can feel all the despair in that enlargened "GONE". *sighs* This also represents the book exceptionally well, IMO.
What do you prefer on the back of your hardcovers? An excerpt, a logline or something else entirely?