It’s amazing how some book covers just shout from the shelves, grab your attention, and demand your focus without looking at anything else. I don’t know why certain covers are effective, they just are. Of course, the whole effective thing is highly subjective.
One book cover that just sucks me in every time I go to the store is Gun Show Nation: Gun Culture and American Democracy. I haven’t read a single page of this text so I don’t know if it’s any good or not. I don’t know (although I can guess from the dust jacket description) the author’s political opinions on the subject of guns and gun control. So I can’t really comment on what’s inside. But the colors, the lighting on the guns, the wood grain of the stocks, constantly entrances me.
By the way, if you’re interested in learning why some book covers work and others don’t, there are some educational book design websites out there. Foreword: A Book Design Blog and Book Covers both do a great job. And uber-book designer Chip Kidd has an official website dedicated to his work. Although Kidd’s website is a tad limited right now, they claim a much more expanded version is in the works.