Of course. That's what the cover is for. I usually look for a title or picture that looks interesting, and for the name of an author that I've heard of. If any of those catch my attention, I'll pick it up and see what it's about. If it sounds interesting, then I'll buy it.

Sometimes the book sucks in spite of a cool cover, but books are cheap, so that isn't a big deal. And I'm pretty sure I've probably missed a few good books because the covers sucked, but maybe I'll see it again and I'll recognize the author's name the second time.

Also, "rent" or buy? Do you mean "borrow" or buy? I'm not familiar with renting books.