For me the cover is not so important when I buy a book. First I check the author and then I try to find some reviews for the book (try as much as possible to avoid spoillers). If the subject sounds good enough, then I go and buy it.
I had some 'painfull' experiences with the book covers.
) They looked nice but the book simply sucked. So I decided never judge a book by its cover. (and this applies also in my daily life, as much as possible).