One book I picked up almost entirely on cover was Slave to Sensation by Nalini Singh (I say almost, I'd read her name somewhere but knew nothing about her or her books). I saw the book, the cover caught my eye, I liked it, got the book, loved that, and I've been a fan since. So picking a book by the cover does find one some gems (although it also finds the dross, sadly).
Recently I was in the book store & I saw the new UK covers for her books. I bought her latest one (Kiss of Snow) but on the way home I couldn't help thinking of the differences between the US & UK versions. I should say up front I have no problems with any of these covers. Authors get very little input into their covers Nalini's been lucky :)
One other comment I would make is that both US & UK covers suggest white men, readers will find that is not the case.
You can see full covers here: US and UK. Two very interesting takes on the same series. Regardless of cover I seriously recommend the series :)