There are these things called word clouds, which are various graphical representations of the concordance of a text. For example, here's one for this very blog, in the shape of a dog (click for a readable version).
Somebody (Thunder Bay Press/Canterbury Classics) has hit on the idea of using these to make the covers for their Word Cloud Classics reprints. Each book has significant words and phrases lifted out and arranged in the covers. It's a simple idea, and done quite nicely. I'm not sure they're my cup of tea, but they look quite appealing.