Three unprepared books are handed to a spectator for examination. He chooses one of them for a test (in this version, you can even do the test with all three books at the same time)! The spectator then picks a page at random from the chosen book and memorizes one or more words that are on that page. Being an accomplished mind-reader, you know immediately which words your spectator is thinking of and you write them down on a slate before making them known to the audience.
A masterly principle of operation makes this remarkable trick simple to perform.