I just tried it on my Droid. It brings up the standard Google search widget and you can type your search string or touch the microphone icon and speak it. I used "Gulliver's Travels" and tried Lilliput and Brobdingnab with no success. Then I made it easier and tried "species". This time it got it right and found the word 31 places in the book. It brings up a list of text snippets with your search string highlighted. You touch one of them and it immediately goes to that point in the book, again with the search string highlighted.
Cool, but is it useful. Maybe...