There are, I dunno, maybe 1,000,000 words in the English language. With a book cipher, almost all books will produce gibberish words not on the list. If you find one for which almost all words are magically on that list of 1,000,000 words, you win.

I get the appeal of the notion that some second grader could stumble on the winning book and claim the prize, but this article is like halfway between cryptographic fantasy and reality. Google suggests there are only 130,000,000 books in existence, which would be more than easy enough to brute force if we had access to all of them. Furthermore, there is a clear success criterion. The limiting factor is that not all books have been digitized, but if the book is relatively well known, it should be.

I'm surprised someone at Google hasn't just put this whole thing to bed by now.