One could use a smart phone to look things up on goodreads, maybe? It seems like somebody could even make an app to do that. Though I don't know if computer image recognition is yet up to the task of "recognize all the books given an image of the shelf", or if you'd have to scan individual bar codes.

(I rarely buy from used bookstores these days, but when I do I'm more likely to get books I read years ago and want to reread.)