Yeah, cover is everything. Take a look at an example from my writing.
This is my original cover for The Oort Perimeter that I did myself. This is also the same cover the limited edition has. FYI, I couldn't hardly give away my book when it had this cover.
This is the one my publisher did. It pops a whole lot more than my attempt at a cover did. Now when I go out to book shows and other events, people just about maul each other to get the book. ^_^ So yeah, same book, two different covers, two entirely different results. It's yet more proof of how covers sell.