A while ago I was pointed to a superb website called Wordle (http://wordle.net) which takes any text you like, counts up the words in it and presents it as a word cloud - an array of words where the size of the word reflects how often it occurs. You can tailor the output to use different fonts, vary the layout and so on.
I have found them very effective for getting a feel for a whole book. Here's a look at my latest book, Upgrade Me:(Note that the image is significantly bigger than this in the original!) And here are two more, of Light Years:
And of The Man Who Stopped Time, my biography of... I suspect you can guess who: